What microstepping do your external drivers support? You may find Arduino/RAMPS too slow to drive them at high microstepping, meaning you will have to either reduce microstepping and accept increased noise, or reduce maximum travel speed. See [reprap.org].
Duet and Duet WiFi can both drive external stepper drivers from the expansion bus (4 for the Duet, 5 for the Duet WiFi) - although the Duet WiFi is probably overkill for your application because you wouldn't be using the nice on-board TMC2660 drivers. In theory you should level-shift the step, dir and enable signals to 5V, but users report that they seem to run just fine from the 3.3V signals on the expansion connector.
Duet and Duet WiFi can both drive external stepper drivers from the expansion bus (4 for the Duet, 5 for the Duet WiFi) - although the Duet WiFi is probably overkill for your application because you wouldn't be using the nice on-board TMC2660 drivers. In theory you should level-shift the step, dir and enable signals to 5V, but users report that they seem to run just fine from the 3.3V signals on the expansion connector.