I test fired my weapons at rocks, and where available, with mods. When fired, the weapon muzzle climbs. In some cases enough to miss the target, and the longer the range, the more pronounced. Auto weapons climb significantly and there is also lateral round dispersion, and again the longer the range the more pronounced. Stability reduces climb and lateral dispersion.
Even with increased mag size, you are still going to be reloading before the mag is empty to max rounds available. If 40 rounds are not enough, a rethink may be required. And having the suit mod for extra ammo capacity, 'cos you are going to burn through ammo.
However, it all comes down to personal preference as to which mods are the best. Go with what you feel comfortable with, bearing in mind that mods cannot be changed. If anything, do not add one of those mods until your experience tells you which one you really want.
Steve 07 (whose usual CMDR's Maverick loadout is a noisy C-44 and Tormentor [audio masked and noise suppressed]).