Yeah the SMG is definitely OP, probably a function of it being the weapon I used the most.. but the sniper is also pretty strong.
Also yes the bullets come at you pretty quick when you go into certain rooms - IMO enemies need a small delay before activating when you walk into the room, something I've already added for a post-jam patch and it feels a lot better.
Unlocking weapons is an interesting idea, but ideally they'd all be fun to pick (and then you can choose upgrades and a build around their characteristics). I don't mind some being a bit stronger than the others, as you can pick a worse weapon to have more challenge, but it just feels bad atm.
Thanks for the feedback :)