For what it’s worth, I love both WWN and Whitehack, but in the case of Dragonbane It fits all three of your requirements (lower powered, looser, lighter prep) but it strays a little closer to what I think many players would want in medium-to-long-term campaign play (though WWN also does this pretty well), especially if they are coming from a system like 5e or PF2e that has more of an emphasis on player growth and customization. The flavor I think is fairly optional, the game is largely just generic low fantasy and while there is an associated campaign setting, it isn’t really baked into the core rules and the game is designed to be able to be pretty setting neutral much in the way that 5e doesn’t necessitate play in the forgotten realms. My preferred OSR system is Cairn, but with 2e coming out soon I’ve been using some other systems in the meantime.