Security Mudi V2 (GL-E750V2 vs. invizbox Go

Hi, I am a layman, have a basic question. I am deciding which portable router to buy and would you be so kind to reply how does MUDI V2 secure my devices when MUDI V2 is connected to public wifi, e.g. without VPN. Is there a default firewall, with or without VPN?
The guys from Invizbox claim that connection is completely secure when Invizbox Go is connected to e.g. insecure WiFi.
My question concerns specifically security, not privacy.
Thank you for answering.

Security with all routers is fine as long as they are running in routing mode. So that’s not a problem.

But: Privacy is waaaay more important when connecting to a public Wi-Fi. Without using VPN it does not really make sense.