first of all, your game is absolutely amazing. it's a joy to play through it every time
no bugs to mention, so i guess i'll focus on the balance of the weapons
railgun ammo is very scarce, and considering that it takes a while to charge it to pierce through buildings decently, it honestly does not feel reliable enough for a primary weapon during a mission long term. it's so powerful that it almost feels like a secondary weapon to deal with powerful enemies, not something you would use against tons of minions and weaker enemies.
it also happens VERY often that i mistakenly press LMB not long enough, and waste a cartridge with nothing to show for it.
the grenade is kind of situational. i can see it being useful in some circumstances, but most of the time i would rather just destroy the obstacle between me and the target with whatever machine gun i currently have equipped rather than having to press x, press it again and then wait for the grenade to finish its arc and reach the target
the scatter gun felt pretty wimpy. the scatter itself is pretty small, and by having to wait between each shot it feels like another inferior alternative to the machine guns, and the increased damage does not make up for it.