1) Don't go by the wattage, go by temperature. Some rooms are warmer, some are cooler, different states vary in climate...90-ish on the warm side, 72-76 on the cool side so you have a thermal gradient within the tank that allows the leo(s) to thermo-regulate (they can't regulate their own body temp. because they are cold blooded...they need to be able to go to the warm side if they are too cool and vice versa)
Also, belly heat is typically more important because they use belly-heat to digest food. Most people use a "UTH" or "under-tank-heater". Its a little pad that emits heat and can be placed under the tank. NEVER use heat rocks!
That said, I use a 100 watt my 20 gallons -- a red nocturnal reptile bulb (don't use UV...use red or blue nocturnal bulbs)AND I also use a UTH with each caging set-up. And I live in California = Hot, mild weather. I have the heat mechanisms on timers so I can use one, both, or none of the heat sources. For example, this morning as it was getting hot out, I just had the UTH's on and the overheads off. Now its frickin' HOT outside and I don't use central A/C so all heat agents are off. At night, I need both the heat lamp and the UTH's on for most of my reptiles.
2)I put the water on the cool side because if its anywhere near the overhead bulbs, it evaporates in like 2 seconds.
3) Cacti are fine. But best not put a spiky one in there. Try succulents. Oh, and Aloe is fine but the crickets, roaches, and worms eat it if they get to it...
4) Use a humid hide. Too much moisture can cause respiratory issues...misting is fine in moderation, just watch humidity (again, dependent on the climate you live in). I always keep himid hidea in all my cages. To be honest, some of my leos never use them. With them, I am more likely to mist when they're shedding.
5) Um...a 'high-yellow' and a 'Blizzard' are the SAME species - Eublepharis Macularis, otherwise known as a "Leopard Gecko". All leos are E. Macularis...unless you get into E. Afghanicus and the leo subspecies debate. Anyways, this doesn't matter because your leos are captive bred 'blends'.
BUT...never put 2 leos of different sizes in together. That's just a recipe for disaster. The bigger one will bully the smaller one into not eating and might even eat it. Leos are best kept alone. They don't need or like 'friends'. Males fight...often until one is dead. Male Female = eggs and forming eggs places a lot of stress on the female -- can easily lead to MDB and other vitamin deficiencies as well as take its toll on her weight.
6) Sand...the age-old debate. Sand should never be used with baby and juvenille geckos. When sand is accidentally ingested by the leo, it builds up in the digestive system causing a major "clog" (if you will)...this is called Impaction. It is common for leos to accidentally eat sand when eating their prey. Impaction is very often fatal and generally a bad deal.
I am sure your sand/calci-sand bag says its fine for leos. It isn't. And if it says it is mostly calcium carbonate, etc. and can be digested/is digestable...that is not true.
Anyways, it is up to you but most people use reptile carpet or paper towels to avoid killing their leos. I admit that one of my leos is on carpet but has a small "sand box" in there for him to play in (he freaks if he can't dig and gets all stressed). I'm taking the risk.
Lastly, remember to dust your crickets, worms, and other bugs with a calcium/vitamin powder.
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Too many Leos
1.0 feline "Spot"
0.1 canine "Tika"
