My estimates based on my research before DNA testing:
25% Cornwall (English)
This will definitely take time to unravel. Here are some questions for my follow-up research:
1. What is the classification of the ancestors who lived in Cornwall, England? They were there for hundreds of year up to about 1850. My theory is that Ancestry has them classified as "Southern England" and MyHeritage as "Scandinavian".
2. Are my "Miller" families (in Pennsylvania) from Scandanavia rather than Germany?
3. What ancestors are the Spanish/Portugese (Iberian)? Both tests have at least one great-grandparent that is of this ethnicity, yet my research to date has not found any ancestors from this region.
A good place to start will be to use the DNA match feature to see the ethnicity classifications for my known matches. More to follow...