Hi....
Why are you using riser if it's just one card?
Short answer yes... it can be close to 50MH/s (if we are talking about ETH)....
It depends if you have LHR card (it should be written on the box).
"What is Nvidia Lite Hash Rate technology? First things first—what is LHR? Nvidia LHR graphics cards detect when they’re being used for Ethereum (ETH) cryptocurrency mining and automatically halve the “hash rate.” Without diving too deeply into the weeds, this makes LHR GPUs less profitable for potential mining purchases due to their higher power draw relative to the now lower hash rate. The idea is that if LHR GPUs aren’t profitable for miners, they will be purchased by gamers instead."
If it's not "LHR" there are a lot of tutorials...