An orthodontist recommended moving my bottom teeth first with invisalign before moving the top teeth (in order to create a frame for the top teeth to move to). is this an unusual treatment plan? will this create an awkward bite during treatment?

Your orthodontist knows your occlusion better than anyone on this forum. Orthodontic care is often completed in phases, so this treatment plan could be correct for your particular situation.

The lower arch is the contained arch. It's common to create a framework to support the superstructure. No, this is not unusual. That said we cannot examine you to arrive at informed clinical opinion. Assuming you are seeing a fully qualifiedOrthodontic specialist, he/she will be able to best answer your questions.