Yes, all items are editable, deletable, and shareable. Technically you don't need to make a listing to have a shop page, but no products will come up when people land on your profile. You'll also be able to edit your shop page in settings.

And at the moment, Amethyst and Coracle both support NIP-99 listings (which nostr:nprofile1qqs2xugc5jyguqkj36rk0syv4tmnkjdtmtperttl7x9rqjy3ustdcvcpz3mhxue69uhhyetvv9ujuerpd46hxtnfduqs6amnwvaz7tmwdaejumr0dsq3camnwvaz7tmjv4kxz7fwd46hg6tw09mkzmrvv46zucm0d5yx7efd uses), so you can make listings from any of these clients and they should show up on the others.