Just a quick comment set points of on off t-stats typically allow for a 1 degree up or down shift. The probe accuracy is low typically (as far as I know all) is with in 2ºF up or down which can increase the error to 3 degrees. If you are using a set point that will directly effect the snake this must be taken into account. It is way I always recommend 90º over higher temps it keeps a space of safe temps. Constant time over 95 but before the point where burns can occur the snake is not able to digest properly and will have issues related to the temps. It isn't a flaw just the way they work they allow spikes you must account for them. UTHs against glass protect against the gain while the t-stat is at full power but it cannot balance against probe error.

Hot spot temps should be set at a point keeping in mind the possible errors in correctly working instruments. Most digital thermometers used in the hobby have the same 2º up or down error. It might be or not but this is the range the manufacturers accept as accurate. Planning for this error is prudent. 90-91 is a good range unless you have a more accurate instrument (check the specs but generally speaking the price will let you know how accurate it is. There is a reason why the price range is very large and why a lab grade thermometer cost so much, accuracy.)