[2022] Will the Nintendo Switch version run at 30fps or 60fps?

Is the Switch capable of running Temtem at 60fps?

Nope.

Temtem could run on the PS4, and that's not the reason why it was dropped from PS4. It was due to us being a small team and not being able to handle all current platforms, as each new platform is a new layer of specifics and complexity and we're short on time&hands. We focused on the latest ones because we wanted to ensure the best possible features and longest life for the game. Hope this helped!
Still, keeping expectations low is the best way to be pleasantly surprised later :)

It will be a custom setting similar to the currently Low one on PC, but we don't have yet the full details since we're working on the optimization and trying to squeeze as much as we can.