Hi, welcome to the fun!
For tiles, most folks posting have been using the cheap field tiles from box stores like Home Depot, and the laser blasts thru the thin glaze and into the porous body of the ceramic–great for coloring, not so good for function of the tile. Though I think some have found a sealant–hope they answer here!
I’ve only played with thick high-end tiles with very thick glaze, and the laser only reacted with the glaze and did blast through it into the body. Drawback I couldn’t color the design, but I didn’t want to, the single color suited the designs I chose, but upside was the tile was still intact and functioned as a tile. (These were tiles left over from a kitchen tiling project, which I got at a bargain price at a building salvage store–Habitat for Humanity is another great source for good tiles at bargain prices!).
So alas you’ll need to dig a bit through some threads–but even so, plan on using at least one tile to test various settings–use a small design so you can repeat it across the tile with the various settings to minimize how many tiles you have to test with!
Easier to start with a lower power and work up, as you can always etch over an area again if it’s too light (as long as you don’t move the tile or the artwork in the GFUI).
And you might find it works best with a masking film, like this: