I feel like with Soulslikes there's really only one rule of thumb and that is that FromSoft's games are still the best of them, even with the many imitators that have popped up over the years.
These are genuinely some of my favourite games ever made, even in spite of how obnoxious their fandom and the way people talk about them have become.
Since you mention not liking the idea of playing something slow and clunky, you'd probably prefer the newer titles over the older ones and while I have to assume that going backwards through the series would be pretty awful, that'd still make either Sekiro or Elden Ring your best bet.
Sekiro is shorter, plays faster and is generally an all-killer-no-filler kind of experience, but while its world design and feel are definitely that of a soulslike, it's combat is actually really unique and generally considered very difficult to learn, so that might be a problem if you want to get an idea of soulslikes as a genre. That game is kind of its own thing.
Elden Ring meanwhile is just... I mean that game is ridiculous.
Prepare for at least like a hundred, maybe a hundred and twenty hours of playtime if you want to see everything there is to see - and that's without the DLC. Whether that's a good or a bad thing is up to you.
(I think it's kind of a problem, personally)
I have my problems with that game, but there's a reason it's such a massive success and so many people got into the series through that game. It's a luscious masterpiece of an experience.
In general I'd also advise you to ignore the Souls community, as that scene has become... well, I find them pretty insufferable overall at this point.
Also also, just speaking for myself here, but I have the most fun with these games when I go into them without spoilers and when I try to get lost in the experience, so I tend to view them less as action games and more as RPGs in that sense.
Whatever you choose to go with, I hope you have a great time!
(I really need to stop rambling like this when I have a headache, I hope that was at least somewhat comprehensible.)