Vlad FYI, I don't have a way to record with a high refresh rate, but I just compared between both Safari and Orion on my M1 iMac and my M1 Max with Promotion. Promotion makes a significant difference with Orion. It's still not as smooth as Safari/Brave/Chrome on Promotion. I'm using a Logitech Anywhere 3 mouse, along with Mos app for butter smooth scrolling. But Orion with Promotion is managable with Promotion. Without it, it's not.
Smooth scrolling with Orion on my M1 Max is not as jumpy as on the M1 iMac, although it's still not as smooth as other browsers, but I do not use a mouse with my laptop. I suppose this means the refresh rate helps with smooth scrolling, but this probably was already known.
If there are other apps you'd like me to compare Orion with, I'm happy to. I don't quite understand why it smooth scrolling works with some apps, but not others. It's the same with PDF Expert. Very jumpy, to the point that I have to a trackpad on it. This is also the same no matter which smooth scrolling app I'm using. I've tried a dozen or so.