for a number of reasons, i wouldn't worry about the mastic (that might take a long time to dry out). one can now safely add mastic into the large gaps, between tiles, and leave room for grout to be added later. The Main Thing here is to make grouting easier and more likely to proceed trouble-free and give good results, that you will be satisfied with. Only a DIY can do this. A pro would not come back for one more little step when they could finish it all off in one go. So, this is a happy time, for you. You get to do a better job than a pro might do. Be happy. Don't worry.

The only ones I've had an issue with were Marazzi, and that was from several years ago but over a period of several years, and Florida Tile, which was from awhile ago too. I can't recall having touched Florida Tile since. Marazzi, I think they have gotten better. The issue with them back in the day was the tiles were just so varied in size. Open a box, stand the tiles on edge (like a deck of cards on edge) and it shows how out of square and varied in size they are across each dimension. I can't say the last time I used Marazzi...maybe last year in 2010? But they were pretty much standard then, I had no out of the ordinary issues. Some tile is only rated for wall use, some wall and floor rated. If the tile has a "glaze pattern", some are applied with screens, like silk screens. Look closely and you can see the screen grid within the glaze. Also, ask how often the pattern repeats in a box. A manufacturer might only have 7 patterns or 15 patterns. In a large room using a tile with a low number of patterns, the repetitive pattern could be apparent after the tiles are set. Through-body versus a surface glaze could be a consideration regarding cut edges. For the most part though, porcelain is porcelain. 2" and 3" squares will both conform to the pitch changes in the shower floor. Most shower drain covers are 4" squares, which nests nicely within a field of 2" tiles. 2" tiles will also give more grout lines, which can aid in foot traction and minimize slips in the shower. There are myriad ways to do a sink backsplash, there's no hard right or wrong. But sure, a tiled wainscot can look lovely, especially with a pedestal sink that shows off more of the wall. If you go that route, take the added wall thickness into consideration when positioning the toilet flange in the floor.

It used to be that 1/16th was called out for rectified tiles. With the new specs for manufacturing, you start getting more variations in tile size. Even in rectified, believe it or not. The new installation recommendation, which has actually been around for a few years, is to have the grout line 3-times the size of the variation within the tiles. This usually comes down to an 1/8th inch grout line. Lippage can also be an issue based on the pattern. A stacked pattern might not show lippage whereas a running bond could. The larger the tile, the more chance you have of lippage with offset patterns. That's all due to the tiles not being perfectly flat. A slight warp, pillow, or pringing (like the pringles potato chip). The grout needs depth. Otherwise it'll just pop out. So a 1/32nd gap with a beveled edge, you may not have durability, because the installer may not pack the joint (if there even is an actual joint) with grout. So: Not to dump on the guy who plans on going 1/32nd...but I'd nix that. Someone who tells me they're going with 1/32nd, I think they're just going to lightly butt the tiles together and get whatever grout penetration they can. And it'll likely be nothing more than topical grout with very little actually packing whatever gap there would be between the tiles. With the new specs, 1/8th inch is the new standard. You could still go 1/16th if the tiles and pattern allow for it, the installer is comfortable with it, and it's called out in the specs...but I'd not advocate going less.

(seal first? or put on wall first?) Either or. It'll go quicker if you seal once they're on the wall. You just have to make sure you put plastic down on the grante, especially if you want to use an enhancer. Seal with something like Stonetech impregnator pro (is this an enhancing seal?) Impregnator Pro is only a penetrating sealer. If you want to enhance the stone, use the Enhancer Pro. I think I need to use 1/8" grout lines since my little glass accent tiles are actually a bit bigger than 2" (so they'll have almost NO grout line around them. IS THIS OK?? You're going to have a tough time with an 1/8" grout joint and tumbled marble. You might want to open that up just a bit to 3/16. That little extra will make a big difference with respect to the sizing of the tile. Grout, being careful to clean it off the surface of the tiles before it dries. (How careful do I need to be on the glass tiles?) It should be fine. do I need to build the wall up a bit with something else, If there's that much of a hook at the end of the wall, it wouldn't hurt to float the end of the wall with a little thinset before you begin the installation