Seems like you can. So since there’s no more points in it, Groot MB is now more like the “get all my Hadron Enforcers and shot multipliers setup” multiball now.
Yes, they definitely carry over. The button flashing at the start of your next ball lets you know. Remember too that you get at least two smart bombs for each completion of targets. It’s sometimes tough to not pound the button when a ball drains. It will help you finsih modes, but they are much more valuable in MB (and II). Resist the temptation.
The first post suggests it prioritizes left most shots. I think that may be only during modes, not during MB. In MB, I think it gives you the most valuable shot, no matter where it is on the playfield. You can no longer collect the double super in groot MB with one, although the value isn’t nearly what it was on old code.