I have it set for 99 and with a 24 hour circ pump in 80+ temps, it gets to 101. As Backpains said then you can control the temps a little easier by opening up the cover to let the heat escape. My wife likes the temp at around 99, I like it at 101. I tend not to go into the tub when it's too humid out.
As far as chems, all chems should work about the same as before except possibly dichlor - the lower temp may let it linger around longer.