Good news - the screws do indeed control hot and cold water level
Bad news - they are both already opened to the max
Good news - the cap actually does pop off of the end of the handle allowing me to unscrew and remove the handle exposing a valve of some sort (looks like the pic below)
Bad news - there's a lot of calcium build up in there and no matter which way or how much i turn the plastic ring thing, it isn't making the water hotter when i put it all back together and test it.
Worse news - By the end of my tinkering, I noticed some drops of water coming down the piping inside the wall. I hope i haven't really screwed something up in there. I closed the water shut off valves to that bathroom for now ... DIY and I don't get along.