There’s some diagnostic info when in game through the battery sidebar menu, I think. You can use that to see frame rate and other performance benchmarks.
I usually just google or YouTube some way to improve whatever game I’m playing on deck. Usually, someone has already done the leg work to figure it out.
As far as I can tell, this product never panned out. It was backed by 132 people to cover 150k GBP in 2017. It was called the “Cyclotron Bike”.