Hydro is simple and effective, that is truth.
About temps in water:
@20'C trichoderma dies and other good micro organisms are starting to die. For example, if you keep your rez 18-19'C, use trichoderma, benificial becteria and fungi and rise rez temps rapidly to 21-22' -you see rapid PH dropdown, that is because trichoderma started to die and created more acid environment.
@21'C water itself is not taking O2 anymore, that means that roots have harder time to breath, also anaerobic bacteria is getting a good chance to live and thrive in that environment, escpecially if it's more acid.
Roots like ir cool, you can get healthier plants with normal tea temps.
Just few thoughts