In this case you need only one router and I believe you'll like better the compact size RT-AX86U Pro, similar to your RT-AC86U. The second 2.5GbE port you perhaps don't need with your 500/500 ISP is coming with much larger footprint device. Single router works better than AiMesh.
Obviously
@TheLostSwede is your source of information. Read through the rest, but do what he says. When you bring the router home and your wife sees it - do what she says. Perhaps GT model version with RGB lights is going straight back before you even plug it in, in original packaging.