There is valid arguments to start with AGGA or with MSE.

Personally Id do MSE first solely based on this:

1. It gets you some forward growth that is trully skeletal and not just alveolar bone remodeling and teeth tipping, which would further allow a better AGGA result.

2. Allows for a much better tongue posture which is what AGGA relys on

3. You can try protracting your maxilla with MSE and if it works maybe you'd skip AGGA all together.

Now there is the other way around:

1. AGGA always finishes with the controlled arch braces to close the gaps, push the teeth forward and widen the palate. So maybe doing AGGA, MSE thn braces would cut on the time spent. MSE would probably be tricky with the open spaces, loose teeth and the back teeth pushed further back due to AGGA? IDK, not a professional

2. MSE before AGGA would take double the time and makes no sense because the controlled arch phase widens the palate. Lets not compare braces with sutural split.

Id go for MSE and AGGA after. It makes more sense to me this way.

But to be honest both procedures together will probably be more expensive and psychologically demanding thn a surgery.