Right now 75 is still kinda low. For my temp cycling for females i keep room no lower than 78 at night and 81 during the day.
Theres 2 diff flexwatt 3" at 2 diff wattage's. Either way they do run hotter due to being smaller ie less space for the power to travel, thus heating faster. As long as you can maintain a 90-92 inside the tub ur fine