Thank you both for your replies. That is fine but it seems like that makes it impossible to lower the amount of villagers who live on my island...If I ever got the maximum ten villagers, then I'd never be able to have less than that, apparently.
I guess this pretty much answers my question. So I would have to scan Amiibo villager on day 1, and then have unwanted villager agree to move out on day 2, who will then leave an empty plot on day 3 which is when Amiibo villager will ask to move in? And then Amiibo villager would take over unwanted villager's empty plot?
I understand that having an Amiibo villager replace another villager is easy when the town has the maximum ten villagers, but my town only has eight, and I was just wondering if it's possible to replace one of my villagers with an Amiibo villager without permanently increasing the number of villagers who live in my town.
But it seems like it wouldn't be practical because apparently I'd have to somehow plan it so that my unwanted villager would ask to move out the day after I scanned the Amiibo villager :/