I was wondering if you would consider doing a listbuilding article or just tips using only classic/mini Marines as a constraint.
Seeing as the official Templar range is classic, and many Templar players are mini marine nostalgics from the codex days.
(also personal OCD with mixing models of different scales)
You are also the only publication that focuses on the boys in black, it would be grand.
First, the HQ units. Honestly, we're running classic marines here anyway. Captains/Chaplains/Lieutenants with Jump Packs, High Marshal Helbrecht, and Chaplain Grimaldus. The only other HQ you really might take right now is the Phobos Captain, but he is an outlier. You might also see an inquisitor here, but that will be another post. The reason? Mobility. Our forces do better when they move around the board quickly, offer up their buffs to similarly mobile units, and get into fray. Everything else is selling our chapter tactics, doctrines, and stratagems short.
Then we have troops. Having no access to primaris, that leaves us Crusader squads or Scouts. Technically, we also have Tactical squads...but you're likely only to use them in a fully mechanized transport build (rhinos/drop pods). The most competitive choice here is scouts for a number of reasons. First, their points cost makes them much more efficient in double-battalion detachments or brigades. Second, scouts have a fantastic special rule called Concealed Positions. This allows you to effectively decide your deployment after your opponent puts their models on the board. Huge advantage, as you will be able to deploy defensively or aggressively depending on your match-up. Third, there are several stratagems that are unique to the Black Templars that target our scouts and make them much more effective. Crusader squads also have a new rule that is a boon to the neophytes in the unit, but the crusader squad prefers to be fielded in larger numbers. This means you're likely to be footslogging, which is not always competitive if you're not moving at jump pack speeds. Fortunately, we have some tools to get us across the board via Litanies, Frontline Commander, and stratagems. You also want those larger squads so that you can hopefully absorb some of those casualties on the way to your target. Losing some weapon versatility with the Crusader Squad makes it less of an attractive objective holder and using them in a mechanized list means you will be eating a ton of points for that mobility. Ultimately, it comes down to whether you can afford to build around a larger Crusader squad or two; or the Scouts using Concealed Positions, but having less durability. I tend to lean towards Scouts.
Now that the more simple choices are out of the way, we'll look at the units that are really starting to get sticky for choices. Let's look at the Elites first. This slot has a ton of value in it for classic marines, including two of the best units for us: Vanguard Veterans and Company Veterans. The Vanguard Vets give us a legitimate close combat threat that is highly mobile, versatile in its close combat weaponry, and has some stratagem support to make it more lethal. Utilizing those jump packs, you can often avoid enemy bubble wrap and never get stuck in a combat you don't want to be in (no penalties to leaving combat with FLY). You can also smack FLY-units out of the sky in close combat, which is hilarious to imagine; though against most Flyer-role units, you'll be hard pressed to keep up with them with their extreme speed. Company Veterans hit those versatile notes as well, being able to be armed with a variety of ranged options as well as close combat weaponry. The downside is these guys are limited to 5-man units and do not have jump packs. Sadness. The other competitive pick here is the Assault Centurians. These guys, armed with Hurricane Bolters, are death incarnate. They are grossly under-costed and are very hard to eliminate. If they hit your opponent's lines, game-over. However, they are slow as heck. They need a way across the board, so Land Raider Crusaders are where its at since we don't have the redeployment shenanigans of the Raven Guard or advancing that White Scars can do.
The fast attack slot is a little bit easier here, as there is only a couple of competitive slots here. Land Speeders and bikers, specifically Scout Bikers. The former suffers from a -1 to hit to its weaponry if it moves, but its very fast and has a nice complement of long range weaponry. This will be important to help eliminate anything that might outrange your forces. Alternatively, the Land Speeder Tempest will be an aggressive close range weapons platform with additional durability, but can be critical late in the game. The Scout Bikers are huge in that they can pump out a ton of close range shots and are very cheap. Excellent anti-infantry. These two are your best bets.
Next up is the heavy support slot. So there really is two units that are being taken in competitive games right now. Thunderfire Cannons and Eliminators. Obviously, since Eliminators are primaris based, we cannot use them. So that leaves Thunderfire Cannons due to the stratagems available to Space Marines. However, they aren't very efficient spammed in your lists. That opens up some other options with the list. We have the Devastator Centurians which can effectively eliminate any unit on the drop, especially with their grav stratagem, but are ridiculously expensive. If you need something dead, these guys can do it. But like their assault counter-parts, they need transportation. Land Raider Crusaders are able to transport the units of doom across the board, while having a ton of shots themselves. They also lend themselves well to our newest stratagems, allowing their occupants to get into combat without the threat of overwatch and reduce the ability of your opponent to hit your unit in return. We also have Relic Leviathian Dreadnoughts which are stupidly good, but require you to have another non-relic unit. They are also a little on the expensive side of things, but well-worth the points if you can fit it in.
Finally, the Flyer slot. There really isn't a whole lot to look at in this slot as everything is too expensive for what it does unless you're playing Iron Hands. Why? Because you are likely moving each turn and that reduces your to hit rolls by one. That is a serious hit to your shooting efficiency. Stormravens used to be the thing, able to pack quite a bit of firepower with some transport capacity, but "Boots on the Ground" basically prevented them from impacting the objective game, which was a huge nerf. Being a flyer isn't as good anymore, as many infantry choices are able to fly and engage them in close combat, where they fold like a wet blanket. If you decide to go with a unit here, you're really looking at the Stormraven for its transport capabilities and using the weaponry as a bonus. A secondary choice would be the Stormtalons. But there are better choices in other slots and these guys will eat up your points quick, which deny your ability to fill battalion and/or brigade detachments.
Now that you have a brief look at the best units in the book, how do we build those lists? Brigade or Battalion detachments are a must here. Start with your Teeth of Terra Captain and build from there. Chaplains are usually a pretty good place to start, but you need to remember that you have to be on the board at the start of the turn to utilize their litanies. Jump packs should be obvious here, as walking is bad. Scouts fill out the troops slots, then take Vanguard Veteran squads. Trust me, they are worth every point. The rest of your force is going to depend on whether you used a battalion or brigade. Honestly, its going to be difficult to build an effective brigade without using Primaris marines though, due to how cheap they can be. Take those double-battalions and you can fill your list to taste!
So there you have it...we are definitely competitive using the "old" marines. This is just a small sampling of the most competitive stuff, but you can use most everything in the book now. Especially the HQ, Elites, and Troops slot. Angels of Death is that good, especially when you add in our chapter tactics.
Good luck and thanks for reading!