Here is a question about UX on an iPhone vs iPad
I need to have a data entry for the users name, and I can do it one of two ways
have a single field where they enter their name [Last, First] or [First Last] or [First] any is fine
have them enter First name in one field, and Last in a second field
The issue is space, which of course is quite limited on an iPhone5 (and just slightly better on the 6/7/8 and X),
So the question is, does the average users name going to be displayed well in just a single field. (not a problem on iPad of course)
Apple (and others) seem to lean towards the 2 field method in apps I can find that collect names (CONTACTS is an example)
I don’t have a Caption followed by a textfield… its just a full width textfield with a cuetext
There should be enough space for separate fields unless you’ve got the rest of the view filled with other things. Maybe you need a separate view where you edit/add user information?
Then personally I would recommend option 2 with separate fields. As you note, that is more visible to small width device users, and if vertical height is not a problem for them (or scrolls) then height is not a problem on larger devices either.