It looks like you should be powerful enough to run 480p at a reasonable FPS. The next thing I'd say is narrow down the problem. Do you have any other cameras you can run at a comparable resolution and FPS to rule out that it isn't your hardware?
After that, since you have a Reolink, you should review this thread:
viewtopic.php?f=10&t=25874&hilit=reolink which is the most popular for Reolink. Maybe there is some setting you can change. E.g. changing to source type: libvlc instead of ffmpeg on ZM might improve the stream quality, or you might change what stream path you are accessing on the camera. IIRC, some settings had better success than others, but read the thread. I don't remember exactly.
It's always possible there's something in the camera stream that ZM can't work with. Does this choppiness happen with ffmpeg from terminal, and vlc from gui? Look for errors in the output.* Are you running anything else on the hardware? (disable X, have a minimal system, don't run ZM in a virtual machine**, etc). Make sure you update to the latest stable release. 1.30.4 does not have the same camera compatibility*** that 1.34 has. So use 1.34, or whatever is the latest even numbered release.
*
https://wiki.zoneminder.com/Ffmpeg has a flag for debug mode.
**if you are careful, I'd venture that you can run small installations on a VM, but generally it's bad practice. Large installations would be a bad idea, due to VM CPU overhead which I assume is slowdown. I don't know enough about VMs effect on CPU instructions to say 100% though. Docker / Containers are better for ZM.
*** Different ffmpeg libraries