Why do you need multiple router boxes? I have one Mtik router in my office with multiple vlans. APs are mikrotik and unifi. Switches are mikrotik and unifi as well.
One vlan for office, one for guest. One cannot see the other once they are segregated via vlan with proper firewall rules.
Router 1 is on ground floor, router 2 is on first floor, router 3 is on second floor.
One AP would not be enough, considering the house is huge and reinforced concrete walls do not help with signal boost
So, router 1 is main router, has DHCP Server and NAT, while the other routers act as AP and switch.