Does it apply to all non auto rifles? Even laser, plasma etc?

The general consensus is yes, and shotguns too.

They definitely do. The damage on my laser sniper went up the last time I invested into the rifleman perk. I actively checked to make sure.

It does but I have found the rifles getting heavier in my inventory. Granted I keep upping my strength every few levels it's mainly for scavenging. I'm beginning to think I should have gone pistols instead, just to shave off a few pounds. I wouldn't carry so many rifles though ammo is in short supply so I have to keep cycling out weapons as ammo presents itself. Also, some mobs have high resistances forcing me to use a different type of attack.

I was pretty sure it does.

I've been putting into Rifleman & Gunslinger as I have .50cal sniper & 10mm incendiary pistol with a combat shotgun for back-up.