Opted to take the safe route and use the Mapei primer. Interesting product, like rolling on a very thin slurry.

 

Your plan is good. Usually wall tile in backsplash areas aren't subject to moisture or abuse. Be sure to use white thinset as gray will cast a shadow that you don't want.

Oh, with glass tile, be sure to buy glass tile blades for your wet saw. You may go through a couple doing it as glass is a different animal. To keep from burning the glass, I usually cut half way through the depth one way and turn it over to cut the rest. With 1/4" tile you may not experience it. Just want you to be aware of the "gotchas".

 

It's not necessary to use the primer or even that thinset. A little sanding would have been fine. I personally would use "mastic", i.e. the newer vinyl versions of it. I see no reason to use thinset, let alone the Adeslex which is designed for glass tiles that don't have the white backing on them. Putting white backing on tile, then using a specific glass thinset, is just belts and braces and there really is no point. Mastic is far more convenient to use in this case. It is recommended to use a white adhesive, but all mastics are white as far as I know.

 

Thanks for the advice, I have a bucket of Omnigrip that the orange box store sold me, but was watching some Sal videos on YT and he said to avoid it so I ran out and got a couple bags of the Adeslex. I saw in the product info for the Adeslex that it's not for tiles with decorative backings as well. So this glass tile should go in fine with the Omnigrip like you mentioned, the newer vinyl mastic in a bucket.