Lower growth removal

Now is probably a good time to do so actually. She looks to be going into bloom and pretty much done with veg so you're safe brother. Just obviously don't take to much, she still needs leaves to make those flowers! Hope this helps.

You can defoliate whenever you like! I usually take off any leaves that are sitting in darkness at the bottom, as I'd rather have strong air flow around the stems. As you say, you don't want to remove too much when you defoliate, otherwise it will slow your growth. However, your plants will bounce back quick as long as you're still in veg - it just takes a day or two and then you'd never notice what you did! I do my main defoliation around the same time stop I flip to 12/12 and continue removing any leaves blocking light to budsites leaves right up to 10-14 days after the flip, depending on the strain. As you're running autos I would recommend that you finish all your LST/defoliation once you see the first signs of flowers appearing and edge more on the side of caution with regards to removing leaves. Good luck!

I usually give my plants a good defoliation about a week before I put them into flower. This gets them setup for fast growth during stretch without wasting energy on lower limbs, as well as giving the plant enough time to recover from the defoliation before flipping lights.