Hi!
Yes you can do both! How powerful led are you going to add? I've heard that adding too much lights in middle of flowering can turn the plants to reveg. I doubled mine but still went good so...
Also I've read that plants mature little bit faster when the lights on time is lowered gradually and what i do is that during flowering every two weeks I take 30mins off from lights so 12/12, 11.5/12.2, 11/13, 10.5/13.5, 10/14
and 10/14 is the final I finish the girls!
Don't know if it helped but I'm satisfied with the end result either way!