yes form level and global level in general Settings) it would exactly like submission url does, I mean the value specified on a form level should override the global one.
yes the order must not be changed so if we decided that we add an extra column for media files after the existing one you would need to add such a column manually after every single media column not at the end.
right, a form should be sent but values might be mixed a bit.
every option might be hidden you can do that in Admin Settings before you give anyone such a device to work, so we can do the same in this case.