I also need to mention that a hexblade dip is probably the single best dip in all of 5e. Free martial weapons, shields, and medium armor proficiency, CHA to attack and damage, and hexblade's curse (prof to damage and improved critical against a single target per long rest) is absolutely incredible for just a single level.
On the topic of Wyll, doesn't he also have an extra proficiency that his build typically isn't supposed to have? I *believe* it's weapons proficiency in rapiers but I'm only like 80% certain.
Yes. Fiend Warlocks only have light armor and simple weapon proficiency. Also IIRC RAW you can't get weapon proficiencies from customizing a background, only tool and skill proficiencies. That being said I'm pretty sure most DMs would be fine with letting a player get a proficiency for a single weapon type from their background.
