Octalink BB length question, but may apply to all bottom brackets?

I'm doing a budget build on an older Norco Fluid. It came with junk components, Acera 3x crank. I put an older XT crank on it but the chainline is way off. The chainrings need to come closer to the frame and there is a good 10mm of extra space to do that. The BB is a 73x126. My question is, if I buy a 73x121 BB, will that move the chainrings over by 5mm? Problem is, the non drive side crank tightens up within a few mm's of the BB, like it should. So that side has no room to move. So do all BB's have the same spacing on the non drive side, and different lengths apply to the drive side only? I see the Octalinks come in a 126, 121 and 116. In my mind I can use a 121 or even 116 and solve my issue.Thanks for any help and wisdom.