Hmm I also tested #1. For science. Crafted the SMG with different parts and aimed at a SGS sentry, from the same tile.
Results:
(Excuse the messy copy paste table)
Steel Cat 8.6 Normal % Burst %
plain 78 34
laser sight 88 39
forward grip 78 42
compensator 78 46
grip+comp 78 54
l.s-+grip 88 47
l.s-+comp 88 52
As we can see, laser sight increase hit % of normal shots by 10%, just as expected.
However, the forward grip and compensator does not increase burst presicion by a flat 10%, 15% or 25 %, but rather 8%, 12% and 20%. Furthermore, the laser sight also add 5% to the burst fire hit %, cumulative with the others when combined.
When changing the distance/base hit%, the burst fire hit% from all components also changes.
In conclusion:
-Laser sight is pretty cool, it also helps with burst fire, though not as much as the forward grip or compensator.
-Burst fire hit % calculations are pretty complicated.
-Use Rapid Reloader/Silencer and Smart Module anyway.