Hi, I hope you are well...
My solution was to create the database that will collect all the information in text mode (all fields), and then I called different SharePoint lists connected to PowerApps with the dropdowns. Finally, the "Update" formula field is related to the value selection of the selected field and it will make the record in your SharePoint list co-related to the dropdown fields. You can also perform the Distinct and Filter in the Items fields of each dropdown so that it brings the information you require.
For example:
I have a field called "Region" and a field called "City" in text mode in my BD_Sharepoint. But the information for "Region" and "City" are in another SharePoint list called "BD_Country".
Finally, I create the form in PowerApps, and I delete the "DataCardValue" from the field to replace it with a "ComboboxCanvas".
In that ComboboxCanvas for Region, what I do is: In the Items field, I apply the formula: Distinct(BD_Country;Title) where "Title" is the name of the region.
In the ComboboxCanvas1 for City, what I do is: in Items, I apply the formula Distinct(Filter(BD_Pais; ComboboxCanvas1.Selected.Value = Title);'City) where Title is my Country and City is what I want the combobox for the field to bring me.
Finally, in the Update action for each card, what I do is make my record the Combobox's value selection. For example, in case 1 for region, my Update will be ComboboxCanvas.Selected.Value
I hope I have been of help.
Regards
