After playing this constantly the past few days (and even topping the ladder on two different alts) I feel confident enough to share some of my thoughts on the meta. It's pretty fun and doesn't feel super unbalanced. There are some things I feel we should collectively keep an eye on, though. So here they are:
Magearna
The Magearna shitposter has prompted me to action. I am of the opinion that Magearna is currently the best mon in Alphabet Cup, overall. That isn't to say I think it's broken necessarily, but it has a panoply of good sets, even if each individual set can't accomplish everything. Besides all of its standard OU sets, you will also see defensive and CM sets relying on Milk Drink. These usually use Moonblast as their main attacking move and are often running fire coverage (usually Mystical Fire). The standard Draining Kiss set exists too, but I've also seen a mono-Stored Power set which seems a bit too reliant on surprise factor to my liking. Specs sets often opt for Magma Storm which can be very punishing to opposing defensive Magearna. There is also tech like Moongeist Beam which is probably the best two-move neutral coverage with Moonblast on an offensive set (although it misses out on certain key things and has a low PP count), Meteor Beam to get another boost and own things like Moltres (again doesn't help much with coverage) and I've even seen AV Metal Burst which can be a nasty surprise if you predict well. I realize I've made Magearna sound pretty broken, which it arguably is, but it's really not a whole lot better than in standard play. Milk Drink is good, but it is mainly only useful on defensive sets which are not walling the whole meta on their own. Opting for Fire coverage on Specs makes it even more vulnerable to Heatran, and giving up Trick makes it lose to Blissey, not to mention that its choice of Fire coverage can be inconsistent (you need to hit multiple Magma Storms to beat down defensive Magearna which is not happening). The existence of Magmazone can be a nuisance to defensive Magearna as well, even if it faces the same inaccuracy issue (note that Mind Blown can be used instead of Magma Storm which usually OHKOs SpDef Magearna). Adding to all of this is Excadrill being an effective offensive mon, as well as random Spectral Thief and Prankster Topsy-Turvy being able to put a stop to its setup, and it begins to feel possible to check most Magearna sets easily in the course of building a team, even if you have to run your own defensive Magearna to do so. That may be centralizing, but there's nothing wrong with centralization unless it's a "broken checking broken" thing which I'm not sure it is.
Excadrill
Probably one of the best offensive mons you can use that just cleans up very easily. The best set is probably SD, EQ, Diamond Storm, Extreme Speed, but DD (or SD + Rapid Spin) sets can fuck over some of the other set's usual counterplay (revenge killers like Specs Pult or Zamazenta-C for example). Excadrill is also a respectable hazard setter, with tech like Explosion or Endeavor giving it a surprising amount of unpredictability for a suicide lead. As a sweeper, it is resilient to usual anti-sweep tech like Thundurus or Unaware. What's more, Diamond Storm has a lot of utility in that the defense boosts it can provide allow it to beat some things it would not normally be able to. For example, Corviknight can only 3HKO with Body Press if Excadrill gets a defense boost, which is why many Corviknight opt to run Cotton Guard to beat it more consistently. Generally, if you pack fat Lando-T, you won't have a whole lot of troubles with Excadrill, but I feel like this thing's list of counters is otherwise jarringly small. I forgot to mention, this thing is a great Sticky Web abuser, too, dispensing with the need for speed that DD or Rapid Spin provide.
EDIT: It's also good on sand of course, forgot to mention, although it's perfectly workable without sand since it doesn't need the speed boost as much.
Stored Power Abuse
The addition of Cotton Guard, Cosmic Power, No Retreat and Clangorous Soul to various mons' movepools allow for some very annoying, and potentially unexpected, setup sweepers. Magearna is here too despite not gaining any of those moves; its Stored Power sets are still very good. These things can be very annoying late game when you don't have the juice to break through them anymore. If it wasn't for Spectral Thief being such a splashable move, these would feel more oppressive, but you also need to consider that Spectral Thief only has half the PP that Calm Mind does, meaning often times your Spectral Thief user can be outlasted. Topsy Turvy is useful for preventing these (except Xatu) from getting out of hand, but that can sometimes feel like a stopgap method, especially if your Topsy Turvy user is pressured to handle multiple mons in a match. Lastly, random Haze users (usually Blissey) can put a stop to this, but that's not the sort of thing that fits on every team. IMO, this is the most disrupting form of "random setup moves" you can encounter in this meta.
Sticky Web
Sticky Web teams are pretty effective, largely because there's a lot more viable Sticky Web setters. Being spashable on so many defensive mons like Slowbro, Swampert, or any Silvally lets your webs setter stick around for a lot of the game. Sticky Web also finds itself on more suicide leads like Accelgor or Sceptile; the fact that they also get other hazards makes them much more viable. And there's some real hard hitters that appreciate the webs, like Excadrill who I've already mentioned, but also boosting sweepers like Bisharp, Mamoswine, and Nidoking which can decimate slower teams. This meta doesn't feel super starved for hazard control as it is, so I don't presently feel Sticky Web is too annoying, but we should keep our eyes out.
That's it. I don't really feel like anything else listed in the Watchlist in the OP is too problematic personally (
yes even Scolipede), but I'd like to hear what others think. Thanks for reading.