I decided to get a 100 watt basking bulb for my 20 gallon tank because the 75 watt was only getting up to about 90 degrees. My beardie is a juvenile so i’ve read the recommended is between 105-110. I placed my thermometer probe directly on the middle of the basking spot & it’s reading 118 so i’m just wondering if this is too hot. He still sits on his rock & is gaping pretty often. Should I go back to my 75 watt?
Go back to the 75 watt. Try adjusting the basking spot temperature by raising the basking spot a little. Measure again. There's multiple ways to adjust the basking spot temperatures. Different wattage basking lamps, different reflector domes, but also just moving the basking spot a little.
I do typically like to run my babies/juvies basking surfaces around 105, but I do agree you don't want it to be 118. Going back down to the 75 and maybe raising the basking surface to be slightly closer should help.