when using Tailscale you can not use another WireGuard based VPN according to their FAQs.

Anecdotally, if I turn off the Advanced killswitch and The VPN killswitch of my main VPN, I can actually bring up Tailscale. But you are right, it does add complexity. Basically I use Tailscale on the server and pFsense firewall as an overlay VPN. It’s also handy if you lock yourself out of the server. A ‘backdoor’ of sorts.