[HELP] Build config recomendation for multiple routers home network

I have 3 routers at my home, (2 are currently dead, but i'll be reviving them soon with a PL2303) and i want to use them to improve connectivity accross my house.
I have a reletavily big and complex house, my main router is placed in the center of the house and the signal strength is not good towards the edge of my house, i wanna use my extra 2 routers in repeater/mesh network so i can increase the coverage.

I have a WR841N V11(dead right now), and a WR840N V2(dead right now) and an Archer C20 V4(running stock fw) (my main router).

I am able to build openwrt by myself, I was running my personal build on 841n earlier when I had only that.

I wanna ask for recomendation for build configs that can help me achieve better coverage accross my house.

I have no prior experience working with mesh/repeaters, I am new to all that, any and all suggestions/tips are welcome