Toxtricity and Porygon-Z should both go. I won't talk much about Toxtricity since others have articulated why it's bad for the tier pretty well.
As for Porygon-Z, all of its viable sets are too problematic for it to stay and not be unhealthy. Choice Specs doesn't have checks and any switch-in is based on an unreliable prediction, and if you have no ghost resist and your best normal resist is something like spd Copperajah, that still takes 31% on average from specs Tri Attack. Unless if you have wish support, mons like Bronzong (which can be dealt with if you run dpulse/sball) and Copperajah do not have the sustainability to properly check these mons. Also, Porygon2 and Milotic leaving the tier don't do any favours. Porygon-Z isn't particularly difficult to get into battle either—the numerous viable pivots we have pair well with it, and while its defences are middling, it can still come in directly against bulkier mons if need be. The opposite player not knowing what Porygon-Z's set is can also result in bluffing Scarf or Specs, and a misstep from the player usually results in a mon having to be sacked in order to find out the set. Scarfed sets are threatening in their own right too, as well as setup sets under veil—if Porygon-Z manages to successfully set up, which isn't that hard under veil—it's near impossible to stop it, especially late-game, which goes for basically all Porygon-Z sets too. While some think banning Toxtricity then reassessing Porygon-Z would be best, I don't believe this will lead to anything useful. If anything, more people will start using Porygon-Z and then it'll truly be far too much for the tier to handle.
I think Mienshao is borderline currently, and I think it would benefit from a suspect test in the future. Everyone knows how good and omnipresent Scarf is: one of our fastest mons; strong STAB with fantastic coverage in Knock Off, Stone Edge or Poison Jab as well the utility of U-turn; invaluable Regenerator ability which is basically what makes this mon too much. But aside from Scarf sets, non-choiced and even Banded sets is what pushes Mienshao over the edge. Life Orb 4 attacks or even Swords Dance sets are ridiculous to counter, as many instantly assume Scarf and go into a fat mon that can tank one hit to scout or a Ghost-type, and non-Scarf sets exploit this style extremely well. While we definitely do have checks to Mienshao, Knock Off or U-turn into a breaker topped off with recovery from Regenerator instantly puts the opposition in the backseat. I don't know if it's entirely banworthy right now, but I still hold the belief that it should be taken into consideration for a test, especially with Noivern, Slowbro-Galar and Milotic no longer in the tier.
While Bewear isn't as strikingly problematic as the mons above, its Fluffy-augmented bulk, high attack stat, and incredible movepool (SD, access to recovery through dpunch, darkest lariat etc) make Bewear an issue. To illustrate how bulky this thing actually is, it takes, on average, about 65% from Mienshao's Close Combat, with no defensive investment and no Chople Berry. While yes, Bewear falls flat when it comes to Special Defence, you can't ignore how easy it is for Bewear to come in against NU's most common Pokemon, namely Copperajah. Even if there are Special Attackers for Bewear on the opposing team, it's rare Bewear would be OHKOed from full, which isn't really hard to maintain given Drain Punch recovery and good bulk. I'm unsure on what mon is more problematic out of Bewear and Mienshao right now; I don't think people have caught onto Bewear as much, whereas Mienshao is everywhere and it is more unpredictable and versatile than Bewear with Life Orb or Band sets being amazing.
Sigilyph's speed, Magic Guard, and expansive coverage have made it a talking point. Calm Mind + Roost sets are incredibly difficult to manage with most go-to Psychic checks, e.g. Steel-types, being rendered useless due to Heat Wave. While Drapion did just drop to NU, it is not coming in safely against Air Slash or Heat Wave. I've also seen some Psycho Shift + Flame Orb sets which cripple checks like Copperajah and Bronzong, and while they are slightly gimmicky, pressuring Sigiyph with Copperajah then finishing it off with a faster mon is the way most teams deal with it. Haze Milotic and Teleport Porygon2 just having left doesn't help either, since these mons were a way to soften a Sigilyph weakness on a team. Having said that, we still do have a fair amount of countermeasures like Heliolisk, Guzzlord, Zoro and more, and as of right now, I don't think Sigilyph pressures the metagame as much as Mienshao and Bewear do.