meet up is OK, but very informal to my ear.
1)
I'm going on vacation for two weeks. (AmE)
If you have to choose between the choices shown, choose
a.
holiday is BrE. I can't speak for BrE.
2)
loomed - no.
loomed up - no.
appeared - yes.
To me, looming has a connotation of danger, foreboding, enormity, and
mystery. It's not the most ordinary of words by a long
shot. I don't believe I've used it in the last 15 years, though I
may have read it once or twice in that same period.
A huge black stealth plane would probably be able to do some looming more easily than a small perky white one!
CJ