Most people use 32qt tubs for adult males, 41 qt for adult females.
6 qt for babies then u can use 28 qt if u want. Me personally i keep my males in 28 Qt's for now. Works fine
UTH (flexwatt is better imo) on a thermostat.
No light needed if ur room temp is around 76 or so because the tub adds a few degrees warmer typically.