If your CPU is thermal throttling then it would explain why you would see a drop in fps while playing games.

There are a few things you can do to lower your CPU's temperatures using XTU. The one that won't have any effect on performance will be undervolting, where you supply less power to the CPU but it (hopefully) remains completely stable without any loss in performance. I have seen elsewhere that people with an i7-4720HQ have gotten anywhere from -60mV to -100mV on their undervolting while remaining stable. Offset your core voltage by -5mV incrementally and test for stability. When you hit an instability just revert your voltage to a previously stable value.

To avoid larger spikes in temperatures, consider turning off Turnbo Boost Short Power Max Enable, or lowering the wattage of it. This will prevent some short performance boosts but should also prevent temperature spikes from said boosts.

And as was mentioned before, you can lower either your reference clocks or your multipliers to lower the clock speed of your card to lower temperatures. Unless you are playing a game that has all of your CPU cores running full throttle with no breaks you shouldn't see much of a performance decrease, if any at all.

Also as an alternate suggestion, how long have you had your laptop? If you've had it a while and you've never given it a good dusting, consider doing so. Your temperatures are going to be poor no matter what if your fans are half clogged with dust and you have dust bunnies roaming around inside of the laptop.