I've heard that 1/8" can go either sanded or unsanded. Any larger spacing needs sanded and any smaller needs unsanded. The scratching would be an issue with glass I am told. I used sanded on my marble that is polished and I don't think it scratched. I will be using unsanded on my ceramic tile that I am using in my BR in the near future because the joint is very tiny. I think with sanded grout there is less shrinkage on those larger joints. I hope that has helped because I just realized that I prefaced every item above with an "I think" or "I've heard".

I had to jump up and down to get unsanded grout. From the get-go I told everyone from the person bidding on the job to the guys doing the work that I wanted unsanded. Then they went ahead and used sanded because a sample board I had done for color was sanded. I could only get small bags of grout in the color I wanted to test in sanded. He said, "Oh, that's what I thought you wanted." As it turned out, I had chosen the wrong color for the grout and had them remove it 10 minutes after it went in. The next time they used unsanded. It looks SO much better.

Beautiful tiling - cute subject. Your pieces fit so nicely together. I always use sanded - no matter the grout lines. Of course, I'm not a perfectionist, and don't pay too much attention to grout lines and andamento - just use the crazy patch method of tiling. I recommend using your gloves, but using a small sponge to spread the grout. I find using a sponge in a circular motion spreads the grout and gets it into all the little places. Then when finished, I take a dry sponge to wipe it down, then a dry cloth, cleaning as I go until the final dry cleanup. After everything is dry, I use a cloth w/vinegar to wipe off the glaze and shine it up. Hope this helps. Welcome to the forum.

Tec Power Grout or another urethane grout woud be my suggestion. It never needs sealing, and won't scratch most stone or glass. It also won't have the more difficult cleanup of epoxy, or the yellowing issue.