This is one I've been meaning to check out!
You probably know about this, but here's link to a nice Pirate Borg character generator: Limithron's Pirate Borg Character Generator
It has built-in flavor (grimdark fantasy), but maybe Deathbringer fits your needs?
It's 5e-compatible. Definitely a stripped down ruleset. Quite brutal, though!
No. You provided your players with constraints; that's different from railroading because they still have agency within the constraints you provided (which, if we're being real, were pretty reasonable - all of the Faewild to explore!). This feels to me more like a "mirror principle" kind of...