Help to access 2 dfferent routers at same time on network, 1 using stock firmware other using openwrt?

Installing and Using OpenWrt Network and Wireless Configuration
6

Hello @jc1685
I tried tested both routers MercSys Mr90 and Archer ax73.

Found Archer Ax73 connects even to furthest room corners.
I have decided to keep and use same.

Can't I install any custom ROM on same.