It's really not that complicated.
They will answer the 911 call, you say this is just a test to ensure the functionality, thank them and then hang up.
Worst case you get some person who complains about the test call, and you calmly explain that you called their non-emergency number beforehand to ensure that it would be OK, thank them, and then hang up.
As for your VOIP location Q: If it has a registered address in another location, you should call that location's local number. Normally you want the correct address registered though, but you could inform them of this directly, as they probably have a database with notes that pop-up based on the calling number.