More elaboration on the question...

If I choose to do NG+, will I be able to undo that choice so I can continue with the current MSQ (when it goes live)?

The reason I ask, I want to use NG+ to level my DNC and GNB, but I may not want to go through all of the current MSQ (or rather, ShB MSQ) before I do that. But if I start NG+, will I be stuck with that until I go through everything again or is it something I can turn off to continue the current MSQ?