I don't know all the mechanics details, but I've played 3-4 thieves, a few hundred hours at hero range...

Honestly not sure about the knock-out influence of strength. One would assume STR (and size) would play a role, but probably not as much as you'd like. My last thief attempt was a duergar binder. Garrotte was still very unreliable, even when enlarged. Side note: don't try binder unless you want endless frustration.

Short of knockout poison, I wouldn't really count on knocking people out as a thief. It's nice as a gamble in certain situations, but you really don't need to KO as your best bet is to either stay hidden, use the element of surprise, hit and run...or just run. The knockout stuff is more niche and for a thug you're best off just going for the damage/maledicts.

I played an arial thief thug and really liked it. Plus high int means your scroll reading goes quite a bit better (i.e., aura, stone skin, haste, etc.-- definitely take the edge to save wasted scrolls). Arial/thug can also be a very strong Villager build.. Acrobatics really shines on a dexy villager but it costs a lot of thief points to be that defensive.

I've taken the full thug path. Honestly, I'd probably stop at third attack and use the points on other niche skills as many of them are quite fun. A few thoughts: gentle walk is a must. Cheap shot rules even though it costs a lot it will seal you so many kills. Can't remember which, I think it's separate (or isolate?) that lets you move people a room away from their group-- really liked that skill. You can move tribunals away from their guards, move them out of town, etc. Double back was also quite worthwhile, I felt...especially if you take knife. Knife can be really useful in sealing kills (and killing tough mobs when combined with gentlewalk).

If you go str build, take the edge that boosts damage on backstab. You can do UNSPEAKS with backstabs. Side note: dual backstab is definitely not worth it in my opinion (literally never fired in pk).

Just my .02 cents. Have fun.