Not sure if anyone here is into the older editions, but I have a blog that covers them. I figured this post and one linked in that post are kinda pertinent to this site, so I am posting the link for it.
Just curious, would you use the Swords & Wizardry White Box game with the Realms?
Sure. WhiteBox is extremely rules-lite compared to 1e or 2e. It might take some handwaving with various character conversions, but it wouldn't bother me much at all.
I'd more likely use the full S&W rules, since the Realms shares most of the built-in world-building of the original D&D supplements over the first boxed set, whereas White Box would be more suited to going off in different directions from most published D&D.