>>95877716You can just play WWN by adopting the mechanics from scarlet heroes.
The fray die and the hit point conversion make any d20 system run as a a duet (or solo)
The caveat however, is these mechanics make the character extremely heroic. If you don’t want this, you need to tinker. Maybe leave the fray die out but keep the HD->HP conversion and damage scaling.
>>95878572The introductory OSE modules are nicely laid out for the GM and would be good fodder for learning. Hole in the Oak and Incandescent Grottos
If it were me, I’d just use the Keep on the Borderlands/B2 but that could be too much scope for someone who is unfamiliar with RPGs
>>95878590Scarlet Heroes handles delving well, and can teach OSR play style (resource tracking and management, time keeping, player agency forward over big plots). But yes as it is a duet/solo engine, even though it chews up old school content well, your characters are very heroic and have to be exceedingly stupid to get themselves killed. However the ref can always tinker with the system to make it more lethal as well.