I made up a warlock character recently and yes, thematically they can be all over the place:
- River spirit patron and proficient with river craft,
- Dagger throwing and cloud of daggers magic,
- Beast speech with animals and pseudodragon familiar,
- Member of a smuggling gang (with secret lord-knight contact), and
- a coward.
It's kind of the nature of 5E characters, you pick race + background + class + subclass, then pick personality + ideal + bonds + flaw + trait.
If you don't stay tight to themes and archetypes you can quickly create Frankenstein's monster. And Wyll's got so much story going on he's near the cusp.
I think they should tighten his character by making him Str11, Dex15, Con14, Int13, Wis9 (yes, he's that foolish) and Cha16; and make him pact of the blade.
