"Obstacle" tokens, in the one haunt I've encountered them, are just used to keep track of where objectives are in a more complicated scenario; I doubt they block LoS in any haunt unless expressly stated.
Regarding locks, the flavor explanation for LoS is that all doors are open and thus that you can shoot in a straight line through them. The locked room's doors however must necessarily be closed while locked, so I'd be very surprised if they did not block LoS.
Interesting. That's exactly the kind of feedback I needed (as we have not found obstacles yet). For locks it definitely makes sense that they do block LoS.
Do other players block line of sight?
Like if I wanted to shoot through two rooms, but there was another player in the first room, would that interrupt the attack?
Players don't interrupt line of sight as ar as I know (you can't really determine their exact location inside the room as to tell if they are indeed in the way of a bullet, so at least in my group we ignore explorers and monsters when testing line of sight).