Is it possible to use the seam catch from standalone (main) application? If yes, is there a overhead? Which one is better in standalone application: use seam catch or use regular try-catch blocks?
Yes and yes, but the overhead should not be very noticeable (of course that all depends on what you're doing, how many handlers you have, etc). I have not run any performance analysis on Seam Catch, but if you're worried about the performance of exception handling, there's probably lower hanging fruit you should pick first.