If I have AdGuard Pro installed, do I need to keep the regular AdGuard app?
No. AdGuard Pro can do everything the regular version can, and more.
When I enable Pro mode in AdGuard settings, I can see the VPN icon. Why is that?
AdGuard Pro needs to set up a VPN to be able to change DNS settings. The VPN is 'fake', in the sense that your traffic is not routed through any remote servers.
Can I use other VPN-based apps along with AdGuard?
If you switch AdGuard to 'Split-tunnel mode' in Pro settings, it will be able to run alongside some other VPN-based apps. We keep the list of compatible apps here