The first movement of the second sonata is definitely playable. It's texturally pretty thick, but with good slow practice and good fingering, it'll fit well.
The second movement... holy crap. I'm just getting into it now, and even the first few bars for the RH are deadly... it's just so awkward (and I have a pretty large handspan)... there are some parts that I'm still puzzling over, and don't feel right even at a slow tempo.
I'm not too sure about the 4th sonata, but I'd say it's probably something similar with the second movement. Scriabin has some pretty awkward writing, and having skimmed through the 4th a little, similar issues came up that I had found in mvmt 2 of the 2nd sonata.
Best thing is to try out a few chunks of each of them. The first movement of Sonata 2 is my favourite writing by Scriabin no doubt. That piece is like candy for my ears haha.