You can only use an Apple Watch with an iPhone. While you CAN use one without a phone, you need an iPhone to configure it the first time (or if you need to reset).

Thry are very locked in.

I always have (stayed woth MP3s) but its harder and harder to even listen to them away from a phone. Major issue I have now is it’s a PITA to play a local library on networked speakers (Echo, specifically) w/out voice interaction being the sole means of use. I just want a tablet with a nice interface to allow me to play music on various Echo’s and speaker sets.

Bluetooth is an option, but it’s not really “home automation” setup friendly.