I don't know what NACS specifically supports, but iirc current superchargers only do 250kW with higher coming at some point in the future. So I assume NACS can do faster, but Tesla actually seems to be behind EA in this one regard. Not that it matters much, nothing that can use an NACS supercharger can even get that charge speed right now.
I don't think this will be a "betamax" situation as you only need an adapter to go between NACS and CCS (provided the charger itself supports doing so - which newer superchargers seemingly will and I'd assume any other networks would as well). That said, I'm not super happy with them going for NACS. Most of the issues with non-Tesla charging networks have nothing to do with CCS (the networks just aren't well maintained and haven't had as long to build out infrastructure). Talk about NACS connectors being "so much easier to use" than CCS(1) is also way overblown, since the reason for larger heaver cables with CCS is due to the cables needing to be longer to support more vehicles, nothing to do with the connector itself.
And convincing an entire industry to move to a new connector is going to be harder than Tesla sticking to its half-walled garden (or eventually switching themselves). Ford tipped the scales a bit, but not exactly in the way I'd hoped.