Suggest exporting each project at close to the source settings, then export the final last step at whatever settings work best for your situation.
One method is to import individual exports into VP using FILE | IMPORT CLIPS FROM ANOTHER PROJECT, which will create a new sequence for each.
After all projects are loaded, click the + sign next to the last timeline sequence to add a new blank sequence. Then in the bin click the SEQUENCES tab. Add all sequences to the timeline, then export that sequence.
Or simply import the individual, exported sequences, place them on the timeline (in a single sequence) and export.
Remember, when exported clips are imported they will be composited - no individual edits will remain.