Hello,

i need some clarification as mentioned in the topic.
What is the benefit of having a mesh network in regards to having multiple access points in same bridge.

I have following configuration:
- One Mikrotik as a main router, non wireless device
- One Mikrotik as an access point, connected to main router using ethernet cable
- One Other brand router flashed with OpenWRT, connected to main router using ethernet cable

Both wireless routers/access points have same SSID configured for both 2.4GHz and 5GHz network.
Is there any benefit of having two of them configured as a mesh or no?

On another point, is it possible to configure mesh between mikrotik running routeros and another router using openwrt?

Wireless mesh networks usually use wireless connections to interconnect APs at least in a part of network. wikipedia article

In your case with both wifi APs connected to centeal router with wires mesh doesn't make any sense. BTW, mesh doesn't change wireless client roaming experience by itself.