Should use unsanded or sanded grout. Also what colot grout white 00 or avalanche?

For polished tile, use an unsanded grout to minimize the chance to scratch the tile. Grout colors can differ by manufacturer, so it is best to go into a store if possible and put one of the plastic sample / test sticks from the grout manufacturer beside and between two tiles to see what you like best. However, even in our board build area, we rarely use pure white grout - it is actually quite difficult to match whites, and almost no white is "pure" 00 white. So a true white grout ends up making warm whites look yellow, and cool whites look blue. So you may lean more to the "avalanche" instead, but test first in the store with the sticks to be sure how it looks with the tile.