Thanks HH.
First let me say I do not know squat about bearded dragons. I am just learning.
I do know a thing or two about construction, renovations and electrical so I will give you my take based on that experience.
I have used a good quality porcelain tile left over from an addition I built. They are stone textured.
All porcelain and ceramic tiles have a glaze that is non porous. So no sealing is necessary. The grout is porous and in my experience even sealer does not make them 100% stain proof. The grout is the weak link in this system so I made my joints as small as possible.
If you lay the tiles loose as many do so that they can be removed for cleaning that is fine but I would think between cleanings stuff could build up in the cracks including water that may have been spilled from a water dish.
I just think a complete closed system with tile, grout and silicone around the parameter is more hygienic and less work to clean. Any dirt, moisture, feces, will be contained on the surface and there will be no chance of it working it's way under the tile.