Very nice job.
Yes, I would give it 2 coats of whatever sealer gives you the look you want, if some get's in the joints, no big deal, seal it all again a week after grouting.
Thanks RD. I had fun tiling this shower, but I'd never be able to do this for a living, I'm too dang slow. It took me 2+ weekends to apply the Kerdi membrane and 7 weekends to do the tile.
The sealing is already getting complicated. We got a small sample bottle Stone Tech's Enhancer Pro and tried it on samples of the various stone. My wife really likes it on the dark stone, but doesn't want it on the lighter stone because it gives it a slight yellow tint. So now I'm grudgingly considering using Enhancer Pro on the dark stone, and Bullet Proof on the light stone. Problem is figuring out how to keep one or the other from running where I don't want it. Ugh!!