I think Apple is transparent about Always on VPN (blocking traffic except over the tunnel) requiring provisioning using MDM tools. Apple Configurator is free and allows anyone to set this up. Any other VPN is just best effort. https://support.apple.com/guide/deployment/vpn-overview-depa...
I hope Wireguard makes it into iOS/macOS at some point. Still early days relative to other protocols of course but it's so much simpler and more reliable (even beyond the security benefits). I use it extensively on both platforms for access to my own networks and services nowadays.
ios/ipad: https://apps.apple.com/us/app/wireguard/id1441195209