A router is required, i.e. the router from the Internet provider. The WLAN is then switched off at this router and the first mesh router is connected to the Internet provider router via LAN cable. The rest of the WLAN is then set up with the mesh routers and ensures stable WLAN coverage.
However, I wouldn't invest in an old mesh system, because for less than 130 Swiss francs there is a future-proof WiFi 6 mesh system from Xiaomi, it can support up to 256 devices and can also be expanded to up to 10 devices. Each mesh router also has a built-in 3 port Gbit switch and the 5 core CPU provides the necessary speed. In addition, the latest WPA3 is standard in the system. Two such sets are a bit more expensive, but they also have much more stable and better technology, which is important for a business.
Xiaomi Mesh System AX3000 (2-Pack)The coverage with the Xiaomi mesh system is very good, with a set of 4 you would have 3 in operation and one as a backup and the built-in switch can easily connect up to 3 devices with LAN cable.
Repeaters are old technology that is no longer used, mesh and good, everything else is just rubbish and technically and practically useless.