Access Points limits in the Sophos XGS model

Why not using Central Wireless? There is no limitation. 

According the size and the business of the company I can agree with You but it's not for our case.

We have a Sophos XGS dedicated only as AP controller for the management of many APs and subnets.

But why use the firewall for managing the Access points in the first place? You could do this in Central Wireless and bridge to a VLAN, which is managed by the Firewall. There is essentially no need to do this on a firewall anymore. Central offers this for free. 

I'm doing myconsiderations about the option you mentioned despite for us, with many different VLANs ,can be bit complicated.

What about the WiFi HotSpot and the creation of vouchers for the guests?  This does not appear managed by Sophos Central.

The captive portal in the Sophos XGS is only for wiFi or can be bound to a network zone ?

I'm doing myconsiderations about the option you mentioned despite for us, with many different VLANs ,can be bit complicated.

What about the WiFi HotSpot and the creation of vouchers for the guests?  This does not appear managed by Sophos Central.

The captive portal in the Sophos XGS is only for wiFi or can be bound to a network zone ?

You can do SSID + Voucher / Hotspot creation in Central as well. Even Social login (facebook etc.) is possible. 

Then you would bridge to a VLAn and the firewall will take over the VLAN routing and other matters.