As above and cut after using masking tape to mark the line and use a diamond blade

Our own experience is that masking tape can be an enemy of the tile and stone world. A little heat, a little time and the glue from masking tape, well, not so good (stone and other materials+masking tape=no-no). Tape is unnecessary. We just use sharpies (dot it) or we just measure and cut (but that's years of experience so don't try that:)

a good Diamond blade meant for glass is what you need. when putting them through the saw, put them on a piece of wood and adjust your blade depth so that it just cuts the tile. if you don't put these little glass tiles on something that supports them, it's difficult to hold while you cut. you can also try cutting them from backside if the glass fragments. that's what tape is used for but sometimes you can just turn them over. practice on a few to get the hang of it.

As for marking them to cut, use a grease pencil for your lines.

If you love the tile, love the kitchen, why not just ask a tile shop for the name of a pro? It's going to be a long time on the wall...yes?

An upholsterer knows a velvet or mohair, is a more difficult job than a plain cotton duck.......so too mosaic blends in tile.

We always use score and snap for the glass. So much easier and cleaner. But as people above are saying you can go either way. I would make lots of tast cuts if I were you and decide what looks best. You could also use diamond file to polish the edges to make it look really good.

Thank you all for your suggestions. We ended up testing out just using a tile saw with a diamond blade and that worked out okay. The glass edges aren’t perfect but that will get covered up with caulking. Score and snap would have been cleaning for sure.

looks very nice Samantha.