Running a set up with cool rooms can be challenging. Herpstats VE300+ Helix or ecozones are all great thermostats basically the same differing menu systems ect. but great solid tools. johnsons and rancos are on off type that will work but often struggle in cool conditions so I'd go proportional all the way they offer the most flexibility.

Cool rooms may need a second UTH for the cool side. If you have done you research (I feel like you have or are currently) you know that the cool side temps should be 80 hot side 90 and ambient air temps in the 78-85 range. To achieve this it is likely you will need to add insulation to the tank and also likely a second UTH (herpstat makes a unit that has 2 probes and will control dual sources) It can be a hard balance to manage. Very do-able, just a balancing act.