Welcome Matthew.
The light signals.... The difference between them is that one is green and flashes the other is red and doesn't
Seriously the difference is flashing green to an airborne aircraft is that they want you back on the ground, having (presumably) just departed. I can't think of why, my Instructor used to say it was that you've departed without paying the landing fee.
Whereas the red to airborne aircraft is intended to say that you will probably be given a (solid) green to land at some point but not yet, so stick around and you'll get down. This contrasts with flashing red which is basically you being told to
off somewhere else.
I couldn't see the point of knowing any of this until my first flight post PPL saw me lose my radio...
As for wake turbulence I would have thought dirty configuration but am guessing
Good luck