Which hardware to automate variable speed exhaust fan?

I got an RVF 6XL exhaust fan that I want to put some smarts in. I was going to connect it to a Lutron Caseta Wireless 4-Speed 1.5-Amp Wired White Smart Touch Fan Control switch, but the manufacturer said I would need a solid state variable speed, speed control that is 5 amps or 3 amps at a minimum.

My option is basically this switch with a knob: FANTECH Speed Control, Black, Brushed Aluminum, 5, 115 Voltage, 2 in Width (In.), 4 in Height (In.) - 15W819|WC 15 - Grainger

Would I be able to install something like a Shelly device between that switch and fan, leave the know turned to max speed all the time and then just use the shelly/sonoff to regulate the speed and on/off? Are there other options to build or customize a switch that would allow me to physically control fan with switch AND use home assistant?

If there is an all-in-one device that can make this happen, I’d definitely use it, I just couldn’t find any IOT option for a 5amp variable speed fan switch.

Just noticed that the back of the fan has the following current requirements (not sure why 2):

  • 115V~ 50Hz 0.80A 93W 2750min-1 10uF 220VDB
  • 115V~ 60Hz 1.15A 130W

Does this mean I don’t actually need a 5 amp speed controlled and a Lutron 1.5 amp fan controller will work?