My situation is with the system info under OpenGL I have the latest Mesa, it shows my video card as an RX560 (which is correct), but for 3d acceleration it shows unknown. My question is should 3d acceleration show something? How do I know I am getting the performance I should be under Linux with this video card?
No.
That information cannot be retrieved anymore since quite some time (kernel 3.12 IIRC).
That would only show the used kernel module btw.
The used OpenGL driver is listed in the lines before anyway.
How do I know I am getting the performance I should be under Linux with this video card?
By running benchmarks and compare? 