I (not a tinc maintainer, but a tinc contributor) have replied to this in the past [0]. Summary: it's not really possible without giving up some flexibility.
Tailscale gets pretty good performance using Wireguard in userspace, with some very clever use of the tun/tap device like supporting TCP segmentation offload. Does (or could) tinc use the same tricks?
Makes sense. Not sure how I missed your comment in the past as I've always been curious if it could be done. Thankyou for answering that. I'm fine with Tinc's performance for my use cases.