John sez:
"send the screws down through the grout lines if at all
possible and use tapcons to secure a cleat. Then it's just a matter of

removing the tapcons and filling the grout lines if you ever decide to
remove it. "

That's the right answer.
Why drill through tile when the grout is so much softer?
In the rare case you need to drill through floor tiles,
use glass bits that are designed to cut mirrors.

thetiler