From best to worse in my opinion

+ 14 Speed + Poltergeist
+14 speed means 110 right... it also means u spend less time clicking shadow sneak and instead click ur stabs more often instead of doing disappointing damage and SD loves it esp since it threatens blace, ada weavile, terrak, zarude, nihilego, garchomp, off zapdos, urshifu-r, victini, and maybe some more in that range. Poltergeist is such a huge upgrade comparing it to the pathetically weak shadow claw which means mimi can actually threaten a lot of pokemon out with its much stronger stab
+2 252 Atk Life Orb Mimikyu Poltergeist vs. 248 HP / 168+ Def Corviknight: 273-321 (68.4 - 80.4%) -- guaranteed 2HKO after Leftovers recovery
+1 252 Atk Life Orb Mimikyu Poltergeist vs. 252 HP / 0 Def Landorus-Therian: 298-351 (78 - 91.8%) -- 31.3% chance to OHKO after Stealth Rock
+2 252 Atk Life Orb Mimikyu Poltergeist vs. 252 HP / 252+ Def Toxapex: 195-230 (64.1 - 75.6%) -- guaranteed 2HKO after Stealth Rock
+2 252 Atk Life Orb Mimikyu Poltergeist vs. 252 HP / 192+ Def Tapu Fini: 250-294 (72.6 - 85.4%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery
+2 252 Atk Life Orb Mimikyu Poltergeist vs. 252 HP / 0 Def Heatran: 344-407 (89.1 - 105.4%) -- guaranteed OHKO after Stealth Rock

+ Flip Turn
Allows it to get the sun abusers much safer and get out of bad MU's easier such as garchomp, landorus-t, heatran, blace, and other bad sun MU's i suck at knowing off the top of my head but generally this helps it get them much safer in instead of wasting turns trying to get a pokemon to pivot them in or having them take damage that could hinder their potential to break through teams

+ 15 HP +Moonlight
Sounds reasonable 80/120/70 bulk is not smth to laugh at and with levitate it has a good MU into many threats and with moonlight it now has access to a consistent recovery that doesnt fall flat. While moonlight is still 8PP it is much better than pain split which makes it very inconsistent as a wall.

+Thick Fat (over Chlorophyll + Will-o-Wisp
Still seems like a worse amoonguss... but tbh i see merrit in this a bit in that its a fat physical wall that can spread status but pretty much worse amoonguss since it gets threatens so easily by its mediocre bulk even then by psychic, flying, and fire types and cant exactly do much back to them unlike amoonguss who can spore them, who also has regen making it much better at dealing with threats late game. This tbh doesnt seem good

+ Contrary
Low speed, low bulk, and doesnt threaten much such as
252+ Atk Heatmor Superpower vs. 0 HP / 0 Def Heatran: 224-264 (69.3 - 81.7%) -- guaranteed 2HKO after Leftovers recovery
252+ Atk Heatmor Superpower vs. 252 HP / 0 Def Heatran: 224-264 (58 - 68.3%) -- guaranteed 2HKO after Leftovers recovery
and there are many better fire types to use such as heatran itself, blace, or victini which dont have massive issues of typing, bad bulk, bad speed, etc which also means teams can often use fire type counters or checks since many teams dont want to auto lose to blace, heatran, and victini which means many teams have ample counterplay such as av torn-t, heatran itself, sp. def lando-t, sp. def pex, volcanion, bulky chomp, dragonite, etc and i dont see this working esp with how dead weight it is vs any offensive team