2 routers in one network, provided that the address pool is full on each completely?

Question

DHCP

At the moment, there are 2 routers with SIM cards, we switch via WIFI and monitor on the collective farm.
It is necessary to connect two routers because the address pool is limited to 255 devices, that is, conditionally, each is loaded to the fullest, totaling approximately 500 devices.
2. The goal is to see all the IPs on the network at the same time on the computer without switching between routers.

Answer 1

Nothing is clear from the question.
Formulate a good idea.
What is right now and what is connected to.
And what needs to be achieved.
Routers do not have a limit of 255 addresses. This is a network mask limitation. This can be changed by expanding the mask.
To combine the router, you can leave 1 main, the second switch to access point or bridge mode

Answer 2

The question will be removed if you expand, for example, to connect 500 devices to Keenetic Hero 4G.
Now there are 2 routers for this.
One network is needed for the monitoring program, and in general, you need to periodically enter the device into the web face.