2 or 3 in Standalone Mode provides all features?

Hi @Peter5_,

Please reference our website product information to find the access point model's support features.

Wireless | Zyxel Networks

Roaming and mesh, in the standalone mode we call it "WDS", are supported for our access points. Below are some FAQs for you to reference.

Establishing a Reliable WDS Connection on Standalone APs — Zyxel Community

The Difference Between Roaming and Mesh in Wireless Networks — Zyxel Community

Hi @Peter5_,

I have all 3-4 APs connected with wired Ethernet. So there shouldnt be any problems?

There will be no problems with the wired connection.

And why is internet needed?

If your network is an intranet and there's no traffic from/to the Internet, then the Internet isn't needed. In addition, since our access point enables NCC discovery by default, you will find the access points try to connect to the Internet. You can disable NCC discovery to fulfill your requirement.