Can you do all of these to fighting targets?

Does the target or thief get the first action after Isolate?

I'm not sure about grapple but I know that you cannot isolate or separate a target that is already fighting. Grapple starts combat with someone who is not fighting. And if you have both grapple and separate when you separate with your hands free you will automatically try to grapple.

I think I remember they can just walk off with isolate. It was niche against trib IF you had someone on the other end of the isolate ready to bash your victim. However, now that there's an edge which will disorient them, it makes isolate seem a little sexier. For my money, though, if I were going full thug, I'd want separate, weapon trip, and cheap shot combo and take the edge that weapon trips on a separate, then use trip from there on out.

Isolate and thief waylay used to be part of the trapper path. So what I used to do was waylay someone and then isolate and they'd be stuck in waylay lag. Of course this is very risky if all members of the group can hit you vs PCs. But it is really useful against necros with a zombie army or orcs with an orc horde or anyone with a pet/mercenary. Except for Trib with vigilance up. Since you can't waylay someone who can detect hidden.

But yeah mainly use it against necros w/ army or orcs w/ mercs/pets after you knock them out. That's just me though.

So underutilized, and only 3 thief points.