I just checked my AMD box and tailscale there can consume ~15% of cpu time when the tunnel is under active use. When it’s not used it’s ~1.5%. But it’s a low power old AMD cpu though (AMD G-T56N), so I’m not use if it compares to Ryzen 5. On my intel machine, it’s ~5% when under active use, and idle at ~0.5%.
Who cares if it already exists, just make it.
Also consider the possibility when the other, more popular projects got enshittified. Now the fleeing users have an option to switch to your project. It actually happened on one of my side project. I made it because I want to try building my own version of X. It got ~2000 users, but later down the road, X got sold to a new shitty owner that waste no time to enshittify it, and my side project suddenly grow to 20,000 users overnight.