I’ve used the Shelly 1 for single switches (lights and bath fans) for years and have never needed to reset one by power-cycling. Both single switches and 3-way switches work exactly the same when physically switching them - no one would even know it’s being used, but you now have the ability to control it with Home Assistant, and the Shelly also has built-in timers and options that continue to work even without HA.
I can’t find my wiring diagram for the 3-way setup I had (different house), but there are schematics out there that show how it’s done. You do need constant power and a neutral wire to the Shelly, and switched output from the Shelly needs to go directly to the light/fan. There are multiple ways to wire a 3-way which makes it confusing, so you first need to open each outlet (and possibly the light/fan fixture itself) to see exactly how everything is wired (which location has the power from the breaker, which location has the line from the light/fan). The Shelly itself may need to be installed in one of the switches or in the light/fan fixture depending on your situation. If you’re not comfortable working with mains power and confusing wiring, hiring an electrician is suggested.
https://community.home-assistant.io/t/shelly1-local-mqtt-with-ha-3-way-light-switch/78690
https://sequr.be/blog/2020/07/intro-into-shelly/#three-way-switch-with-shelly1pm