Recommend smart switches in USA

I recently got a Homey after getting fed up with SmartThings (used SmartThings for over a decade). Smart bulbs are easy but I want to pair traditional smart switches. When I look at the best buy guide (Smart Switches & Dimmers | Best Buy Guide) many of these are UK, not US. And none of them seem to fit in a regular switch box. Ideally, I’d like to pair with my existing Leviton switches ( Leviton Decora Smart Switch, Wi-Fi 2nd Gen, Neutral Wire Required, Works with Matter, My Leviton, Alexa, Google Assistant, Apple Home/Siri & Wired or Wire-Free 3-Way, D215S-2RW, White - Amazon.com) - but my existing switches will not pair with the Homey and I’m not sure why. My current theory is that the switches are currently connected to SmartThings over Wifi and the Homey Leviton app ( Leviton App for Homey | Homey) wants Z-wave - so therefore my theory is my existing switches are not compatible because they don’t support z-wave.

So…if I buy new Leviton z-wave switches, will those actually work (i.e., have people here had success with them?)? But seems like preference is zibee over z-wave? Are there other switches that people have had success with that are the same size as Leviton? Perhaps GE Enbrighten App for Homey | Homey?

When I switched to Homey it was because of my perception of easily identifyable compatible devices - but now I’m not so sure.