If i gear down a turbo to 300 rpm will it have equal or less than torque to a geared up to 300 rpm speed?
Since all of the motors output the same power, if they are running at the same speed, they will have the same amount of torque. Use whichever spacing works better on your bot.
it is worth noting though that gearing down a 600 rpm cartridge will have less friction than gearing up a 200 or 100 rpm cartridge, because a 600 rpm cartridge has fewer internal gears, and you aren’t having any “backtracking” so to speak in your power transfer. Gearing down a 600 rpm cartridge also provides less slop than gearing up a 200 rpm cartridge, because the the slop in the motor is reduced through the gearing rather than increased.
So I would prioritize whatever spacing works best if that is a concern, but I would also try to gear down a 600 cartridge if it’s not inconvenient to do so.