Oh gods, now my brain is obsessing over how Fred would've dealt with them.
But they could take out Angel easy, at least if they caught him in the wee hours of the morning, with that time warp thing (okay, they WOULD have to get that device on him, but it seems there are multiple ways they could do that) so that he's caught out in the day. Heck, just high powered UV (hmm, would the invisibility caused by their invisibility ray make Angel immune to the rays of the sun?). Surely they can do that. ('Course, I could see them doing something dumb like powering up UV lamps just enough that they have to touch, like a lightsaber, rather than creating a deadly beam, as they're as stupid as they are brilliant that way.)
'Course, the Powers could warn AI, and Lorne and other informants could learn of strange purchases on the black market, or people who had been bragging (who could inform W&H just as easily, speaking of which, AI would probably assume W&H rather than the Trio, unless they had a heads up). If encountering any androids, Angel would probably figure it out pretty fast (I'm sure they smell to him) which could get a search started. He'd probably notice that black van a lot faster than Buffy did, too.
OTOH, there are entire chatty rooms on Angel that the Trio could use, and they might find themselves in competition with a competing group of foolish but brilliant geeks. Or having that professor (or whatever he was) that was sending people to Hell dimensions deciding he wants their tech (but how to get it while getting rid of them?), have them dealing with Gwen Raiden (who may work for or against them, perhaps both, though if she already has a rapport with AI then she might sell the Trio out, no matter how unprofessional), and having the Trio find themselves mixing with hardcore criminals that are unlikely to be found in some place like Sunnydale (despite a death rate you have to respect, heck, human criminals at least probably get targeted more by the monsters in Sunnydale simply by being more available at times and locations where the monsters can get at them more easily).
Had to add the part of where Lorne detected the bugs set up by W&H in the hotel because of his weird hearing. That could easily work against the Trio as well.