1: Charizard was one of the top dynamax users when it was out due to max airstream since it increased speed, and max flare could set charizards own sun. Since the dynamax ban its viability has gone way down, it normally has to run heavy duty boots if it doesnt want to lose 50% from rocks, but because of that it cant run things like specs or other items. so overall its not bad but not the best pick either.
2: The main ones I know of are quagsire and pyukumuku in uu but as of rn i don't know of any others. Mainly poison types like drapion and weezing are the premier toxic users.
3: Knock off is much less distributed compared to before, making doublade one of the premier picks in UU. Gurdurr isnt explored but does not seem very good in my opinion. Mr mime doesn't need eviolite and prefers heavy duty boots, as a better rapid spinner or a potential sweeper due to its speed tier. the premier user of knock off is 100% drapion, but there are other choices such as centiskorch and sirfetch'd.
4: Fire water grass cores? I haven't seen all too many but a good fire grass core based around sun is ninetales + shiftry, overall fire types are unexplored and still nothing fair has been seen in my opinion and testing, but it's still fairly unexplored.
5: Cramorant is.. an odd mon. It's stats are mediocore, and overall it doesnt seem like it'd be a good pokemon. but its typing, speed at 85, and its ability gulp missile makes it a super annoying pokemon to deal with just due to the sheer amount of damage gulp missile does at 25% each hit, and potential to paralyze an opponent. I don't call it a good pokemon myself but its one hell of a troll with endure thats for sure.
6: I haven't tested claydol much but it had a bit of time when it was being used as a pokemon with nice role compression, but overall it has a niche, but definitely is not the best mon. It's valueable because of its stab combo, and ability to set rocks+spin at the same time. Levitate can be useful too.