After talking a bit more about PU with some people and playing a game, it is definitely a really fun tier. It actually has quite remarkable playstyle diversity, as it is feasible to play with Hazard Offense, Stall, Sun, Rain, and Sticky Web, I've started to look into Hail since we have things like Walrein and Glaceon which can really appreciate it. I'm specifically going to talk about some of the top threats in this metagame at the moment:
Samurott is a pretty huge one, and I'm going to go ahead and call it the best Pokemon in the tier. It simply has so much worth on a team, whether its the common Life Orb 3/4 Attacks set, which uses strong coverage to back up a high Special Attack stat, the powerful Choice Specs set which is a terrific early-game wallbreaker, or the underrated Swords Dance set which can break past its common counters. All of its stats are pretty good, especially offensively, but it doesn't slouch defensively either as 90 / 85 / 75 bulk isn't really too bad. The Water-typing is also such an amazing typing at the moment with so many viable cleaners to take on the many resists that have tried to tank hits from Samurott early-game.
To carry on the strong Water-type motif, we have Barbaracle and Carracosta, two similar Shell Smash sweepers which can very easily clean up after Samurott. They have a few advantages over each other though, Carracosta has Solid Rock to create easier setup opportunities, priority Aqua Jet to somewhat make up for its low Speed after a Shell Smash, and much higher bulky physically. However, Barbaracle is much faster freeing it up to run Adamant, has Tough Claws which actually makes it stronger, and has a higher Special Defense. Both are still great though, and can be devastating with team support.
Lilligant is an amazing Pokemon in this metagame. Not only does it have ways of beating all the Water-types in the tier, but it has three devastatingly effective roles it can carry out. The first is a Quiver Dance set reminiscent of BW RU, which can setup on things like Samurott and just win games. A tier without Flying-type priority for once! With Sleep Powder, it can almost always gurantee two boosts, getting a QD as a Water-type switches out, then a Sleep Powder, then another QD, then it can just win with Giga Drain / Hidden Power Fire. It also finds a home on sun teams, where it can use Chlorophyll to become a late-game cleaner. Finally, the Choice Scarf set can revenge Carracosta while also having the supremely clutch Healing Wish to restore a weak / statused teammate.
Speaking of Grass-types, it also appears to be a rather dominant type in the tier at the moment. Swords Dance Leafeon is a great sweeper with Leaf Blade, Knock Off, and either Substitute or Baton Pass. It also thrives in the Sun. Exeggutor is another great Sun mon that is incredibly strong with Choice Specs and is one of the tier's better wallbreakers. Defensively, Roselia is bulky with Eviolite and has both Spikes and Toxic Spikes, and is one of the glues on Stall teams at the moment. Tangela is similar but much more physically bulky with an amazing ability, Regenerator.
As for hazard offense, it's pretty hard to remove hazards with such reliable setters and terrible hazard removers. Garbodor is my favourite setter at the moment, it is bulky enough to get many layers of Spikes and Toxic Spikes. However, it can't OHKO Kricketune with Rock Blast which sucks, and has a poor matchup against other common leads such as Piloswine and Golem. Kricketune and Leavanny are Sticky Web leads which support a powerful playstyle with things like Guts Flareon, Guts Ursaring, etc. Kricketune is better though as it has Knock Off and Endeavor. Golem and Piloswine are good Stealth Rock leads, with the ladder being much bulkier but without Sturdy, while having priority for things like Lilligant. Golem loses to Roselia though, whereas Piloswine can potentially weaken it with its Ice Shard. Glalie is one of the fastest Spikes leads, and has Taunt which is a godsend in lead matchups, but it loses to Golem. In terms of hazard removal, there really isn't much. Wartortle, Avalugg, Torkoal, Articuno, Murkrow. Nothing really that special or stand-out in any way, though they do have little advantages; Murkrow is especially promising as it has priority Thunder Wave to stop sweepers cold.
Musharna is another Pokemon that makes this seem all too similar to BW NU. It is a great defensive Pokemon with very nice bulk, as well as a cool supportive movepool with the likes of Moonlight, Thunder Wave, Yawn, Toxic, and Heal Bell. While there are less Fighting-types for it to check and a lot of Pokemon now carry Knock Off, it can still wall common threats such as Poliwrath, Tauros, Golem, Piloswine, and most common defensive Pokemon. There aren't too many other common Psychic-types outside of Exeggutor, but of the few that are viable, Meowstic-M is a huge one, as its priority dual screens greatly help in setup. Kadabra is another strong, powerful Pokemon, though it unfortunately lacks Focus Blast.
In terms of fast powerful threats, two of the best at the moment are Sneasel and Raichu. Raichu has a great base 110 Speed, which allows to revenge kill a whole lot of Pokemon including Barbaracle, Carracosta, and Samurott. Having a STAB attack to take on most of the Water-types in the tier is very beneficial. It's a very powerful, hard to wall special attacker with good coverage between Thunderbolt, Grass Knot, and Focus Blast. With Nasty Plot, it becomes very similar to OU's Thundurus, whereas with Encore it can create setup opportunities by capitalising on something like Musharna locked into Toxic.