In my opinion, I would say Clefable, Aegislash, Dragapult, Excadrill, Darmanitan-G, and Toxapex are top consistent threats for sure. Each proving to be most useful even in the DMAX era. Defensive Corsola-Galar + SpDf Corviknight is a good defensive core that I've seen, read about, & used. There's not really too much to say about it that hasn't already been said except, it does struggle against Dracovish & Dracovolt.
As for question 4 -
Arcanine @ Heavy-Duty Boots
Ability: Intimidate
EVs: 252 HP / 92 Atk / 20 Def / 144 SpD
Careful Nature
- Fire Blast / Flare Blitz
- Iron Head
- Play Rough
- Morning Sun
This is a low-key great mon to use on fat teams as it can blanket check so many pokemon with pure ease. The EVs are quite complicated so, I'll go over why the set is like this & why its Careful Nature even though the STAB move is special (you can still run Flare Blitz but the recoil makes the tank job harder).
Fire Blast is can still OHKO Bisharp & Aegi in sword form, which is great due to this set being able to tank Bisharp +1 black glasses night slash from 80% or higher and takes 54-64% from Aegi's specs shadow ball. Now, with this EV spread you can effectively take the specs shadow ball & still be able to come in on LO Clef's thunderbolt and heal up with Morning Sun while 2HKO'ing with Iron Head (50-56% against the 92HP speedy set which is the bulkiest speed set I could find). Fire Blast can also have 6% chance to OHKO Ferro after rocks. Flare Blitz is only useful for SpDf Bulk Up Corviknight as Fire Blast with Careful Nature only has a small chance to 2HKO after rocks on the switch-in (Arcanine switching in).
Iron Head not only great for Clefable but, it is also great to use against Hatterene. Arc 2HKOs w/ Iron Head and Hat only does 40-47% with Psychic (if its running Lefties, otherwise it does 52-61% w/Life Orb), allowing you to stall out trick room with morning sun. A good note to make is that it fails to 2HKO max bulk Sylveon (even if you run flare blitz) but, it can 2HKO bulky Grimmsnarl while tanking any hit.
Play Rough is honestly a fantastic move to use against Hydreigon as it does an auto OHKO. Arcanine tanks +2 Dark Pulse and Scarf Draco. (Draco Meteor does 50-58% & +2 Dark Pulse does 61-72%). This means Arcanine can check Hydrei even if a sub is up but, not if sub is up while at +2. This set can prove to be useful for stall against Sub Plot Hydreigon, which is an overall menace to it as talked about in previous threads.
Not only does it blanket check Hydreigon, Aegislash (both special & physical; tho head smash can OHKO), Clefable, Hatterene, Bisharp, Offensive Grimmsnarl, and Speedy Clefable but, it can also check Darmanitan-G choice locked in the wrong move, Dragapult (Arc does not handle Specs Modest that well but it does handle Timid) and Cinderace. This set is decent in Dmax era & will definitely do a lot better now that DMAX is gone.