Yaaaay! You can now add oversampling to ANY plugin or entire FX chains in REAPER!
This is one of the most exciting additions to REAPER in a while.

How to apply oversampling?
Just right click any plugin from the fxchain window and select <key>FX Instance Oversampling<key> and choose one of the options. You can go up to 16x.

You can also apply it to the whole chain by selecting <key>Chain oversampling<key>.
What’s oversampling and why would I use it?
Oversampling makes non-linear plugins like saturation, distortion and compressors sound more clean and pleasant at the cost of using more CPU power. This doesn’t mean it’s always better tho, it’s fine if you prefer the sound with oversampling off.
Try it out in some of you synths, guitars, saturated or compressed tracks and see if the difference is worth the extra CPU power. Altho you can always freeze the track and get the sound without the cost of CPU.
Here’s a little demo:
Don’t take my word for it, though. Listen to Dan!
Please watch Dan Worral’s video on this. This a super interesting and extensive topic. He talks about why sometimes it’s not a good idea, when to use individual vs chain, some warnings and much more!