Thermostat controls your heat source.
THG and FlexAWatt are sold by the foot so as long as they are EXACLY identical you can run multiple on the same thermostat as long as you dont overload the stat.
UTH is only for a regulated hot spot and does nothing for ambient air temperatures.
Depending how cool the room is you will either need to warm the room or use overhead heating.
You might look at radient heat panels.