If you need to change the size of the lookup fields on a page, you can do it through the section wizard. Here is the article for more details. Please refer to the paragraph 'How to set up field location on a page'
Of course, all of the dropdowns can be modified. You just need necessary Lookup in the Lookups Section, open it and Add\Edit\Delete the values for the dropdown.
Just to clarify, not just the calculations are coming Out of the Box, but the dropdowns (including Stage, Country, Source, and Status for example) are also OOTB?