It really doesn’t matter how narrow you go in loud RF environments. 5ghz spectrum is maxed out pretty much everywhere other than very rural areas, and can only get so narrow. Even that is starting to change with WISPs hanging tons of cambium and ubiquiti 5ghz APs.
A point to point link over 5ghz will encounter interference no matter how hard you try, trust me. Unless you’re there first.
6ghz works extremely well over very short distances, but even something like tree cover will reduce its connection quality dramatically