Unfortunately, in this case the answer is the standard one for consultants.... It depends.
More seriously. In the case you dscribe I would normally have suggested you move that whole design out of SharePoint and into a relational database like Azure SQL. At least I would have prior to the new licensing announcement for October 1. Now that option may be cost prohibitive unless you already have Dynamics or premium licensing.
If you don't and it needs to stay in SharePoint there are a couple possiblities. First, would be to have a central form that loads up all the key values from the other lists. That way you can have one form with one record and use the values in the field in that record to get records for other controls and child forms. That one central form would also be the one driven by a selection in a gallery if you are using that kind of feature.
The other possibilty I can think of is to try to get all the info loaded from the various tables into a local collection and then drive your forms from the collection (kind of like doing a Sql view or a join to get a data set).
