Announcements: That all depends on your script. You should be able to send a TTS message to any media player
Find my phone: Also here, if you create a good script, you should be able to make your phone ring.
Timers: Timers don’t work on any device, as the timer will run on the device itself. It should work if you issue it by voice on the HA Voice PE
The fun thing about voice in HA, is that you can build anything you want using sentence triggered automations and/or scripts. But for some things you need to build the logic yourself.
I created some blueprints which you can use to get e.g. weather forecasts working. You can find more info here (oh wait, I see @Thyraz already linked to them)