Screen tops are inferior to solid tops with lights mounted on the inside. The reason is simple science. Hot air sucks up moisture, hot air rises. The hot air is replaced by the dry cool air in your room. You'll need a higher watt bulb to achieve desired temps and the rapid loss of the moisture in your cage, due to the air movement, will greatly increase the rate of moisture loss in your dragon (dehydration).
Sandboxes are not a good idea either. Sand is worthless to a dragon. Soft sand is even useless to most true desert reptiles. Beardies don't dig for fun
They dig because their instincts tell them to dig. Their instincts could be telling them to dig for several reasons. One is dehydration due to bone dry environments. Dry soft sand is almost as useless to a beardie as tile is. It can provide security (if setup a certain way, but not aid in shedding,
hydration, or nesting.