Re: Best monitors
Issue with hygrometers are that most of them are not good enough for high humidity area. Doesn't matter where you will place the sensor, with enough time it will not work anymore right. It would help to get semi-professional sensor like from Polyga, but to expensive for just a normal hobby.
For temperatur you could use something like Lucky Reptile Thermo Control II. You could run a heating element with it or cooling fans that go on/off. Also you can control the time for light on/off.
If you have a big rack, go with the arduino/raspberry pi variant(alot cheaper).
Otherwise I agree with @Socratic Monologue.