I really can’t imagine anyone happy playing at 17 FPS…
As people have said, that means your PC is underpowered. I play on average between 30-40 FPS on medium settings using the minimum requirement GPU (RX 570), so for me, you’re using a very weak GPU and apparently you seem willing to sacrifice performance for have better graphics quality that your PC definitely can’t deliver. You’re basically torturing your GPU.
Don’t expect high-quality payware aircraft to be as ‘light’ on FPS as the default aircraft are. Lower your graphics quality or buy a better PC before investing in payware aircraft.