What devices have access to my esim

If I understand it correctly then the number of devices that can access your Personal Hotspot at one time basically depends on your carrier who has enabled Hotspot for your SIM and iPhone model.

On my iPhone 6 iOS 12.4.8 the maximum connection allowed is 3. Beyond that when I connect, I get a popup message which says "Unable to join Network, Try Later"

See the Pic below

Is this your device? If yes, you would know if it has eSIM or not.

If you want to who all are connected to your Hotspot at any given time then that option is not available as yet.