Hello,
I just wanted to put my two cents in about the tile.
The only reason that tile would be slippery is if you use a smooth finished tile, like porceline, marble, glass, etc. I don't reccomend those, because of their slippery factor and also depending on how much heat reaches the tile, some types of tile can become very hot, and will reflect heat instead of absorbing it.
I use slate tile, and other types of non smooth finished tiles. I have had no issues with toes, or slipping, and it keeps their nails filed right down. If your tile is fitted properly in the tank, there is also no risk of nails or toes getting caught in them.
Slate type tiles will absorb heat as well, which can act as a dual function of keeping the enclosure a bit warmer as well as mimicking their natural enviornment.
In the wild, the sun would be baking the ground, so if they move to get out of direct basking light, there is still some warmth radiating from the grounf (floor).
IMO I do not like sand. Apart from the impaction risk, which can be minimal in some cases, there bacteria it harbors is seriously disturbing. The only way to get the substrate comepletely clean would be to wash the sand, drain, and dry it before replacing it back into the viv.
Think about the liquid portion of the poo, and on sand all you can scoop out is the solid matter. All of that liquid will remain in the sand.
I very much doubt that people using sand switch it out as frequently as would be needed. I don't know about everyone else, but my girls poop once a day, sometimes twice. That's alot of bacteria build up even after just 2 weeks.
I started off on sand (that's what the breeder I got my very first beardie from reccomended), and I will never go back.
Just my opinions on the matter.