Im about to start a isp company and i will be havong speed of 20/20 mbps on my site so i have been wondering about how many clients can i connect to that speed?
The number of users that connect depends on a number of variables, one of which is the capacity of the ACCESS POINT and radios to handle the load.
For a basic consumer wifi router, I would not consider 20+ users to be viable. It could do it but the performance would be sub par.
Somewhere about 40 per band on a decent quality device is probably all you will get, although most will say stick to 20-25 max (especially for a 20-20 and an expectation that people will be doing more than just checking emails.)
On the other hand something like this is probably overkill…
https://www.cambiumnetworks.com/products/wifi/cnpilot-e600-wi-fi-access-point/
You may find this useful.
https://www.revolutionwifi.net/capacity-planner/