All transport category airplanes are designed to be very flexible for the operator, that is to say they can decide how to best allocate the available weight. Few if any can take max pax, max cargo, AND max fuel.

Optimal CRJ 200 leg is 1 - 2 hours. Less than that you will be limited by fuel burn down to max landing weight, more than that and you will be limited by the need to carry more fuel.

Wx and alternate requirements can load up the fuel too in some cases.

High and hot is not usually a problem at most commercial airports unless combined with a short runway...TUS likes to close either 11 or 29 at 2100. If you're running late, you might have return to the gate and unload 25 pax so you can use the little x-wind runway The best way to perform that evolution is leave the cockpit door locked and let the gate folks deal with it