What is the best way to know what Hubitat can and can't do

I'm going to have to cancel my holiday then. I'm sure my wife won't mind. :sunglasses:

I am also coming from ISY--is IFTTT the only way to program Hubitat? I want to write routines that are If-then-wait-then, etc. Does Hubitat support this?

Yes. If you can pair your device to Hubitat (Zigbee, Zwave, and even some LAN devices like Lutron or even some Wifi devices) then you have a couple choices of how to automate things. Rule Machine being one, but there is Simple Automations, Motion Lighting, and other simpler apps depending upon what you are trying to do.

You also have the choice to use IFTTT if your devices cannot be directly paired to the hub. There is an integration for IFTTT on Hubitat. Maybe you want to use something like email, or electrical rates, certain Wifi devices, and other similar things.

https://docs.hubitat.com/index.php?title=IFTTT_Integration

https://docs.hubitat.com/index.php?title=Rule-4.0

https://docs.hubitat.com/index.php?title=Hubitat_Elevation_Documentation#App_Documentation