There is no disguise kits in game, as far as i know ...
And no tools proficiency ...
Thieves tools uses Sleight of Hand ...
And i believe the other proficiency you get from Urban Tracker is Stealth ... not sure tho.
So they clash perfectly, you dont stact two proficiencies, nor the game (at least not in EA) gives you option to pick other proficiency if you get one twice.
So ... personaly i suggest switch one of them for anything different.
I still dont understand why cant we change Race for our hirelings.

Lets us play Githyanki as racist as they trully are!