I can't say I agree on the 40-50% ambient... especially not if you're using tubs, getting down to 40% means that you put too many ventilation holes...
Humidity should be 50-60% minimum normally and pushed up to 60-70% during shed.
Tubs until your snake is large enough for an AP cage or similar PVC cage is definitely a good way to go. They're much less expensive, although be aware your ambient temps will be pretty close to your household temps unless you have a 2nd heat source aside from a UTH of some sort. So if you have a cold house over winter, you may need a CHE and 2nd thermostat for winter.
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