I’m not 100% sure but this might also depend which OS you are running on your pi. Did change from SD card to SSD few years back for my home assistant setup (now running with a mini pc) at the time I went for a geekpi adapter (can’t recall exact model).
Try a quick ducduck search “sata adapter #yourOS#” and see if a list come up. Here is one for HA (but surely more models are compatible than the ones listed here) https://community.home-assistant.io/t/working-usb-enclosures-and-adapters-with-hassos/212763
Edit: as for SSD, I went for Samsung EVO model
Sidenote: all SSD will be more reliable than a sd card because they are less sensitive to rewrite counts
Home assistant has a voice assistant but it isn’t a voice assistant. Also, you are correct it is made to control a smart home (at the moment) that also include music threw external provider (or local files) but you can’t search the internet threw it. You can either install it locally or pay for home assistant subscription which include voice assistant threw cloud.