Oh Gawd... if they're even looking at CGNAT I'd make preparations to test before deploying a VPS to run HeadScale or Netbird or less ideally, TailScale, if you're not into self hosting/controlling your own infra. CGNAT is a cheap way for a ISP to expand their pools — 'line must go up' after all. FWIW only Netbird seems to be able to be set to use PQC. The last time I looked @ {Head, Tail}Scale they didn't have it.
Better to have it & not need it than need it & not have it.