Can I choose where my additional fields appear on the product page?

Yes. In Products → Additional Fields, fields are organised into groups, and each group decides where it shows.

1. Click Add Group and give it a Group name.
2. Under Display as, pick Show in Product Details, then Show as Product Tab, Inside Product Description or Inside Additional Details. Or pick Hook (place on product page) and choose a Hook place.
3. Use Sort order to show the group above or below the built-in content.
4. Edit each field and set its Group.

Fields with no group are listed as Ungrouped.