You can either populate the dropdown by using this in the Items property of the dropdown:
Filter(Products, 'Default Price List'.'Price List' = First(BrowseGallery2.AllItems).'Price List'))
Or if you want to first populate in a collection, then you can use this (may be on the OnSelect property of a button):
ClearCollect(ProductCollection, Filter(Products, 'Default Price List'.'Price List' = First(BrowseGallery2.AllItems).'Price List'))
And then you can set the Items property of the dropdown to: ProductCollection.
If both of your questions are resolved now, please mark this and the other reply with the word document with "Accept as Solution" and give Kudos. Not closing out the thread will not anyone looking in the forum for a similar issue.
In the end I found I was running up against limitations that the unique functionality I wanted required. Primarily the limitation I reached resulted in the "Multiple levels of expansion aren't supported." error.
So I tried a different approach and created a custom entity to hold the information I needed. Created a function app to update the information on a schedule and with in a couple of hours my Power App was working correctly.
Thank you all for you suggestions.