Testing has shown that specific placement of waterblocks and radiators change water temps by 2C at most, with alot of tests showing no change at all.
What this means is that there is minimal difference in temps linking your watercooling like this:
cpu-gpu-radiator OR
cpu-radiator-gpu
As with stuffing your whole PC into a refrigerator, this shouldn't cause condensation issues, ASSUMING you don't open and close the refrigerator. And if you're that worried about condensation when cooling your computer this way, just stuff in a bag of that stuff that absorbs water.... can't remember what they're called. If there's no moisture in the air, it can't condense anywhere.
It is possible to use aircooling with peltiers, but bear in mind that peltiers work by pumping heat away from one side to the other. If you can't move that heat from the hot side, the cold side wouldn't get very cold. In peltiers, they always have a deltaC reading, which is the maximum difference in temperature between the hot and cold side. Which means, if the peltier has a deltaC of 20C, and your hot side is 80C, your cold side would be at least 60C. So its in your best interest to keep the hot side cool (which can be done with YET another peltier, which is stronger than the first peltier, and keep stacking them).
But yes, generally huge peltiers take up huge amounts of electricity, so a secondary PSU, or a huge PSU to start with would be good.
Even though your room is pretty hot, I reckon a good watercooling system would be a much cheaper alternative (in terms of direct costs and running costs) to TECs, and you wouldn't really see much of a difference. The key word is GOOD watercooling system, so stay away from cheap systems from thermaltake and the like. My personal favourite is the Swiftech set, which is among the best, but there are good waterblocks from DangerDen as well (I don't think DD does complete WC sets).
If you're looking for budget watercooling, I'd recommend a GOOD aircooling system instead, since those would perform as well as cheap watercooling systems, with less risks and yet lower direct and running costs. At the moment, I'd favor the Tuniq Tower, since its among the best out there, yet reasonably priced, compared to my Tt Ultra-120, which is more expensive since you'd have to fork out money for your own fan. Having played around with both, I must say any performance difference is minimal.