I use my Deco M4's in router mode, connected via Garage (main unit) to my Proximus ISP modem/router. Their physical location is: Garage ==> Gang ==> Slaapkamer where Slaapkamer is much closer to Gang

I want to install a 3 unit system in a private house on two flours for 3 laptops. On which criteria do I decide to use router or AP mode? The TP-link technical explanation doesnt help me. Many thanks,