Depending on the rack some have airflow on the top (ARS, Freedom Breeders), for other there is usually a 1/4 inch gap between the tub and the shelf however I prefer having more airflow and all my tubs have holes. Drilling can crack the plastic I recommend using a soldering iron it will be much faster too.1) i see pictures of racks and it looks like there is no circulation. is it okay to drill air holes into the tubs?
Depends on the snake I recommend to provide a hide see if the snake uses it or not and if it does not simply remove it. Usually younger snakes are the one who tend to need a hide in racks.2) are hides necessary for racks? i heard you don't need them, but i want to provide what's best for them.
Radient heat panel would not work in a rack it goes on the top and you could not slide the tub out, there is also too little room for that.3) heat tape makes more sense to me than using radiant heat panels. what is the advantage?
Cheap power-strip can be a fire hazard they can overheat and melt, if you do so you need to spend the money, but I recommend to have your heat plugged directly in your T-Stat.4) say you have a rack with three levels and two tubs each level. if all six snakes require the same temperatures, is it safe to plug all of the heat into a power expander, and then plug that into, say, a herpstat 1? or is it better to get a herpstat 6 and connect each one individually?
Does not mean you have to have and Herpstat 6, all you have to do is wire your heat tape properly. My racks are 10 high and there is only one strip of heat tape running through the entire rack not 10.