@Dobalina 

That's very easy. I do it now. I previously had 2 routers; my main from my fiber modem is a Linksys WRT3200ACM VPN modem; it provides a wireless 2.4g/5g vpn as well as vpn for some wired devices. (I use ExpressVPN and the vpn software allows me to dedicate some things to vpn and some things to operate in the clear). I then had a netgear router for wireless 2.4g/5g only. It was in the clear with no vpn. Because of some wifi dead spots on the netgear, I upgraded to the TP-Link XE75 router and satellite node. I took out the netgear and put the XE75 in it's place. It gets a 192.168.41.x IP address from the Linksys WRT3200ACM; and the XE75 outputs a 192.168.1.x subnet. All works fine.

 

My linksys WIFI has a totally different SSID and password for it's VPN wifi than my XE75 has for it's wifi for all the clear traffic.

 

There are some things (very few if you know what you're doing) that has issues with "Double NAT" (Meaning one router behind another router); but most things don't have an issue. All of my streaming devices, my wyze security cameras, and so on work perfectly fine. Just have to make sure that the 1st router (connected to you internet modem) knows how to pass the information from the 2nd router out to the internet.

 

And for what it's worth, "Double NAT" in it's own right is actually a very good security measure to stop outside attacks. Instead of the hacker getting through your router and then hitting a device, it has to go through that router, then through another router before hitting a device. I definitely prefer having 2 routers and double NAT.

  @Dobalina It is usually recommended to add the X25 Deco as a satellite to the existing BE85 network.  That would create one large wifi network.

 

What do you want to achieve by creating a seperate wifi network?

I can't speak for the original poster, but for me I use 2 separate networks all the time. Especially for wireless. One separate wifi for devices needing a VPN connection. (Laptop, desktop, banking, financials, etc.) The other for devices that need a clear connection. (TV streaming devices, cameras, IP Phones, etc.). This also allows me to force guests to use the VPN network. (Unless they can't access a particular site).