Not a guru but one typically would use the 7i85s daughter board. Or all-in-one with the 7i95.
Look for the 25-pin fpga expansion connector. I use 7i76e+7i85s combo but many variants will work like 7i96+7i85s.
Ethernet gives flexibility, I tried the 7i76e on the Rpi4 with good result.
I think one can have somewhat faster servo-thread (2-3 kHz?) with pcie, but never felt a need to go faster than the default 1 kHz.
