Sort of, but it takes some effort. In general, WiFi switches don’t play nicely with a z-wave/zigbee hub like Hubitat.
This seems like multiple questions? There’s a built-in dashboard that can be accessed remotely. There’s also sharptools. If you setup homebridge on another device like an RPi, you can see your Hubitat devices in Apple HomeKit; you’ll need an Apple home pod, Apple TV or a spare iPad to enable remote access or notifications though. If you’re looking for notifications only, then you can get that with Pushover, which isn’t free but is worth the small expense.
Yes, with a caveat. There are solutions that could allow you to keep a device on ST, but sync it with a virtual device in HE. So it’s technically possible to have a zigbee device paired to your ST hub but accessible from your HE hub.
I had a Lutron caseta (non-pro) bridge that I used with my ST hub. I switched to Hubitat, got a pro Lutron bridge and I haven’t regretted it for a second since.
