When i'm on mobile data I can barely get it to send imessage. I have a Pi4 right now on which I plan to install it (diet pi seems to have really easy setup for wire guard since i had trouble on the raspios aarch64 lite image, i think headers were missing) but for now nextdns seems to be okay. NextDNS has their own app for iOS but I sometimes have trouble on that too so i just switch DNS and see what works best. The ISP DNS are definitely worse than anything.
You need to install linux-headers-rpi to build wireguard on Raspberry Pi OS - should be good then.
Yes actually I tried it last when the raspios 64 beta was just released and didn't have an SSD for the pi (SD cards are really slow). I plan on adding another pi for building and one for DNS so that if the Pi is compiling it won't slow down any DNS queries (which it shouldn't but you never know).
pivpn makes wireguard very easy to set up.
I found dietpi to offer a very friendly home server setup. RaspiOS is of course great if you want to do things manually but dietpi seems to have taken r/homeserver crowd very seriously.
I'm sure, but for anyone reading these comments thinking that they still need to compile the linux kernel to run wireguard on any debian distro: they don't. For 32-bit, at least. I have not tried 64-bit yet. I'm letting that one marinate.