I've found 100 RPM to be a pretty good target for an FRC swerve steering rate...a PG71 with a 2:1 ratio will get you close and provide plenty of steering torque.
The robot in
this video is running this setup. It's lighter than a fully loaded FRC setup, but we've used the same setup on heavier machines with favorable results.
Medical hoist with PG71 steering for swerve.