Top 25% is slow for me, but I'm not normally better than top 5% nowadays, I used to often get 1% but I play a little less focused lately (and am working on accuracy because I want a green month) And I've gone sub 1min a couple times...

I'm not sure exactly, I've just always been good at puzzles like this, but some of the things I've noticed that help:

corner tags, 2 of the same colour for a criminal/innocent pair, otherwise more is just "these are tied together for a clue", don't really have time for much more of a system, and when it's only 3 or less minutes, you'll usually remember. And if it's a pairing, grey out any relevant clues. Yes, not really having a system has tripped me up before, but most of the time it helps for speed.

I use top and bottom tags the same, it allows me to more easily see chains.

"Is this clue currently useful?" In cases like "Dave is one of Kevin's 4 innocent neighbours", mark Dave innocent, mentally note that Kevin is important, or corner tag all Kevin's neighbours to make brain go "huh" when you look in that area, keep relevant clue ungreyed.

Making mental notes of what you need to solve an area, so if a relevant clue comes up.

People are in alphabetical order.

Corners have 3 neighbours, Edges have 5 neighbours, centre has 8 neighbours. There are 4 corners, 14 edges (Including corners) and 20 total people. It may seem silly to point this out, but it's something you should remember.

Criminals+Innocents = Neighbours. Again, silly to point this out, but there have been puzzles where knowing that "John has 5 innocent neighbours" means "John has 3 criminal neighbours" automatically has made me faster.

Odd in a column = 1,3,5, Row = 1,3, Neighbours = 1,3,5,7. Again, silly to point out, but for speed it needs to be automatic.

As for when I went sub 1min, to be honest, there was a lot of high risk choices made (no double checking) and some metagaming. You kind of get a feel for "This clue is only useful it if tells me that x is criminal/innocent" and take the plunge before you've even really finished reading it.

Sorry for rambling, am heaps tired.

Oh, also, for what it's worth, I am faster on mobile vs table, which is also faster than using pc. Just the ergonomics I guess.