How do I switch to Zwave JS?

You should be able to take your current network key (if you have secure devices), add that to the config for ZwaveJS and just start it up. Well, stop the old zwave stuff first. It’ll take quite a long time to do all the initial interviews for each node, especially if some are asleep, those could take hours to show up properly, or even a whole day. You shouldn’t need to exclude and include everything.

Beyond that, you’ll end up with all new entities, which is unavoidable. So you’ll need to update all the automations and templates and stuff that used your old entities and point them to the new ones. I don’t think there’ll be a migration wizard or anything to automate this, since it’ll be very unique to each and every HA instance. Or, once the old z-wave entities are removed entirely, you should be able to rename the new ones to match the old names so templates and automations work properly again. Either way, you’ll need to update things manually, and I don’t think that aspect of migration will change, tho I could be wrong, and there could be some migration-magic in the pipeline.