They can leave the town world tile as part of their routines, but they can't while following you, and will actively refuse if you ask them while they're not on the town world tile.
This is simply because that feature would require a suprising amount of work to develop and doesn't seem that important right now, so it's low priority.
There's currently hard limit of 7 main characters because Nemo (the model) breaks down after ~4,000 tokens of context/memory.
One token is about 3/4th of a word, and everything the NPC knows, including the short term memory of the current conversation and information about every other NPC living in the village has to fit in there.
Mirel is an 8th character but the other NPCs knowledge about her is located in the same place as NPCs knowledge about less relevant information like items or locations which doesn't take up context tokens.
This only works because Mirel isn't always around. I tried moving all NPCs there but it doesn't work out because it's a less organic way of incorporating information.
A better model, preferably with linear instead of quadratic attention is required for more main characters but there isn't one yet.