I have setup the attached sample file to render Long Hairs (yellow) in one area and Shorter Hairs (orange) in another.
This has been done using Vertex Groups and setting one Hair Particle on one group.
This is the result for Final Render with RPR 2.0.52 (on one GPU because two GPUs don't work).
This is the result in Cycles.
The overall hair is perfectly fine.
However... on the RPR version there are some very odd "Random" hair strands sticking out that shouldn't be there.
I don't know what is causing this to happen. As Cycles does not render these hairs at all.
Sample file attached.