When I used OpenVPN, the VPN had to keep sending keepalives and periodic key renegotiations to keep the session open. This is fine on a PC, but it keeps waking up the radio hardware on a mobile device which is a real battery drain. It's the same as running an app on the background that constantly polls for data, something Android spent a lot of time on fighting to gain better battery time.
I wouldn't hold my breath for official WireGuard support in the manufacturer Android kernels until some big corporations start relying on it but custom ROMs are able to use kernel modules already[1].
Encryption itself should not be much overhead. WireGuard cryptography is based on ChaCha20. While I haven't encountered any hardware support for ChaCha, it's performance is quite good, so good even that Google is requiring manufacturers of very low power Android devices (running Android 10+ Go) to implement ChaCha-based encryption on budget devices [2].
I wouldn't hold my breath for official WireGuard support in the manufacturer Android kernels until some big corporations start relying on it but custom ROMs are able to use kernel modules already[1].
Encryption itself should not be much overhead. WireGuard cryptography is based on ChaCha20. While I haven't encountered any hardware support for ChaCha, it's performance is quite good, so good even that Google is requiring manufacturers of very low power Android devices (running Android 10+ Go) to implement ChaCha-based encryption on budget devices [2].
[1]: https://git.zx2c4.com/android_kernel_wireguard/about/ [2]: https://security.googleblog.com/2019/02/introducing-adiantum...