Very nice! No, driftwood is not too big...but, again its up to you! I would wait since you added so many ferts and the like...ferts, root tabs, usually don't need to be added right away, but shouldn't hurt anything except might get weird readings on tests...ammonia may have spiked but not for long since you have so many lush plants to suck it down!
Again up to you, but light does look less bright on the right...so far, you've done the right thing by putting anubias there...put plants that like or tolerate less light on that side (anubias, crypts, java fern) and then you don't have to get more light.
The shrimp and snails function as clean up crew for algae, dead or dying plants, and fish poop...they will help break it all down so plants can utilize nutrients better and faster, producing more O2 for fish. In a low-tech ecosystem like we are attempting to create with this setup, we need the plants and fish, of course, but we also need smaller organisms, like shrimp and snails, and then we need microorganisms....all these together gets us as close as possible to our goal of a mostly self-sustaining ecosystem!
You're doing great! It's ok that you tore down to make better...just so you know, flourite isn't needed in a dirt tank, but anything will work. Also, if you removed dirt, then this is technically no longer an NPT but it is a hybrid.
I also noticed that we didn't answer your gravel question: yes, you can use a fine gravel for your cap if you hate sand that bad! Read the sticky at head of NPT section as Old Fish Lady has explained this very well.
Did you use flourite as the cap? If so, you have to tell me how it works. I have used sand, gravel, and a combo of sand and gravel as a cap...they all have issues, especially when rushed.
Congrats on gorgeous lush tank!