The 'platform' for the FEIT ones at costco are really well built. They make the Insteon units look like they were a one off hobby project. That's the part that has the power circuitry, screw terminals, etc. The wifi module used to be ESP based but they switched about a year ago to a newer BK723 chip, these can be reflashed with a 'OpenBeken', which is a newer project that has similar functionality to Tasmota but for these newer chips.

The only downside I've seen with these is OpenBeken is not as mature and the units 'hang' now and then requiring a power cycle (like 2-4 weeks). I have some of the older ESP based units that are otherwise identical and they never hang, this has been getting better with upgrades so likely will eventually be fixed.

If you are OK with soldering you can buy the ESP controller modules on Amazon for about $1 each and just replace them and run stock Tasmota (you have to unsolder the module to reflash it either way, so its not a big deal to just put a different one on). The module pinout and electrical interface are identical.