Go back to the store where you bought them. If they can't answer your questions, return the tiles and look some where else. I am guessing your stock comes from a box store (hardware), try a real tile vendor.

Use spacers, your best results will be achieved by getting some sort of gap between adjacent tiles.

If you simply but them together and grout, the bevel in the tile edge might afford a bit of a grout line. But the grout may not adhere to the glazed bevel and the bits of grout could pop off over time.

So go for a gap, and for filling a grout joint less than 1/8" wide, which is what you are proposing, use unsanded grout.

The grout is what locks the whole installation together as a whole. And, the smaller the grout line used, the straighter the wall will need to be. Your proposed layout will lack adhesion strength, even with modified thinset being used to set the tiles. Glass is smooth and slick and difficult enough to adhere without that complication. It will also be absolutely unforgiving of poor drywall work or any bowed or waned studs behind the wall. Put a 4' level on your wall and chart the highs and lows that even a "straight" wall will have. With no wiggle room at all, your installation will look like ocean waves and soon lose it's correct grid pattern.

Thanks, it sounds like I need "real" grout lines. Still, the 4"x4" (I've used in a bathroom, including stand alone shower and a tub) have built in spacers that provide, I estimate, no more than 1/16" space between tiles. The work I've done with these is now about 20 years old and holding up well. The subject brick shape however doesn't seem to have any space other than the bevel, which does go down to the unglazed edge of the tile.

I would in any case plan on a 1/8" gap at the counter-top which is filled with caulk. I notice there is a Jacks (not sure it isn't Jax) type spacer that looks to my mind's eye to be better than the older flat cross spacer. Any advice on the type of spacer?

On a related item, if I cut (wet saw) or break, ceramic scribe and brake, a tile and the edge will be exposed, is it possible to use a polishing stone or other tile cutting tool to smooth that edge, round it off a bit? I know when I hit an interface, including a corner I will use a caulk to close the run...that has worked well in corners where I have the cut edge of the "top" tile facing away from the line-of-sight, making the cut edge almost impossible to see. I'll have to check to see what I did in the bathroom job many years ago when I came to a bull-nose finished edge. I'll guess there must be some cut/broken edges there, I didn't have a wet saw when I did that job.

Just in case one cares to advise, my new counter top is a solid man-made material. Do I have to carefully protect it from any drips of a mounting mastic? Would it be safer to use a thin-set as regards any "splats" hitting the new counter-top? I believe most mastic material is petroleum based, I will guess if there is a latex mastic it may be safer to use over the new counter top. The old bathroom tile job I referred to I think I used a combination premixed mastic/grout...hey, it is still holding both the grout and tiles. That job was above fiberglass tub and shower pan, I didn't see any damage from drips on that job.