RPM ratios and (non)use of reducing gearbox was discussed here https://openinverter.org/forum/viewtopic.php?f=4&t=2137
From experience i can say i have been involved in building a car using Leaf motor with OEM gearbox as well as a car using leaf motor coupled with original transmission, allowing it to shift clutchless.
I got following impressions:
1. Nissan OEM gearbox was clearly calculated with similar car mass and torque in mind. Off the line car feels smooth and there is lots of torque with instant delivery from throttle.
2. Original Mazda transmission allowed use of all the gears. Yes one could driveoff in 5th too, but torque would suffer. The best driveoff was from 2nd, shifting to 3rd for cruising, maybe 4th for going really fast on highway. Downsides of transmission were springiness inside the coupling which would impede direct torque delivery. There was some rattling in 3rd gear which i assume is standard for RX8 transmission where rotary engine is usually ran at.
So I would summarize, transmission is never ideal for electric motor. There is allways some rattling of gears and such anomalies which are now heared since engine does not drown them in noise.
Motors own OEM gearbox is allways considered optimal.