I know quite a few people with this issue, unfortunately, I would get a hold of the devs and ask them to fix it on their side. I say this only because I have heard nothing but issues when regarding streaming.Important information!!!
The cause of the low frame rate is OSBuddy itself. I tried running RuneScape in a different client, and also the official OS client and it worked perfectly without lag/framerate lag.
Now that I found out about this, is there any way I could at least improve my experience a little bit?