How many devices can be connected to a Wifi Adapter?

Computers and other devices on a Wi-Fi must share a finite capacity of resources. The precise limits for how many devices can connect to and use a wifi adapter  depend on multiple factors:

How many access points

Limits of Wifi network scalling

There is virtually no limit for number of devices that can be connected to the Wi-Fi Router, although, some routers have a limit, that allows only certain number of devices to be connected at a time. This can be changed if the router provides the option to change that.

Now, if you connect more number of devices and speed of your internet speed is not sufficient, then it is not practical to connect many devices at the same time. So, connect only those devices that are being used.