If activity level already accounts for calories burned during exercise should I disconnect my fitbit

Not necessarily.

Generally, syncing a tracker leads MFP to compare what MFP expected you to burn (based on all your settings including activity level) with what the tracker thinks you burned. If the tracker sees you as more active than MFP expected, MFP will add calories to your daily goal. MFP uses those estimates - because that's all they are - and tries to keep you at the same calorie deficit and same weight loss weight you requested in your profile.

As long as you're not also manually adding exercise in MFP, there shouldn't be double counting. (Even when adding exercise manually, it can be OK in some circumstances with some trackers, but that's complicated.)

If you'd not adding exercise manually, generally the extra calories you get would be interpreted as your total life being higher than what MFP expected. That could be calories from exercise, or calories from job, home chores, social events, whatever.

Note that the reconciliation will be most accurate at the end of a full day, i.e., adjustments over the course of the day may involve some estimates/projections of what you may do for the rest of the day based on what you've done so far. Some of these things vary by tracker. If you want experienced advice from other MFP/Fitbit users, you may want to consider joining this group:

https://community.myfitnesspal.com/en/group/1290-fitbit-users

If I were you, I'd keep the tracker synced and make sure the negative adjustments setting in MFP is enabled.