At those speeds you will want your numbers as high as possible. You will need to minimally use a 40 MHz wide channel, probably an 80 MHz wide channel. To increase reliability you will want a very clean channel as well as use high gain antennas on your clients to help increase your signal strength vs the inevitable noise.
The two biggest factors will be RSSI and SNR, and of those two SNR is the big stick. If you have a really quite environment you can have -60 dB RSSI and have 30 dB SNR which will give you the oppritunity to have low PER and High PHY rates. For best results you will want your PHY rates to be maxed out (MCS 9) as much as possible, the less time your AP has to spend talking to any one Client will mean that it can talk to more Clients faster.
Other factors, having a clear Line of Sight (LOS) between your AP and your Clients. This doesn’t just mean “having visiblitiy” I also mean that there are not obstructions between your client and AP which will impact the Fresnel zone of your link. (Trees and buildings being the most common)
But if you are in a high noise environment -60 dB might not even be enough to keep an antenna connected to the AP, much less pass a reasonable amount of data.
All that said, the Mimosa Documentation is pretty good about directing you at what you would need for what you are wanting to do: