Can we change our status to MFS after we have began filing MFJ? MFS looks like it may be more beneficial and I'd like to run both scenarios.

[MaryK1]

Yes,  but you must decide- 

You can change your filing status from a separate return to a joint return by filing an amended return using Form 1040X.

You generally can change to a joint return any time within 3 years from the due date of the separate return or returns. This doesn't include any extensions. A separate return includes a return filed by you or your spouse claiming married filing separately, single, or head of household filing status. 

 Once you file a joint return, you can't choose to file separate returns for that year after the due date of the return.