You will retain the same functions you currently have. Even if you buy tow mirrors that are fully decked out - only the power and heat will work.
Power fold is a whole different beast. I'm not going to get into it here because its been discussed in detail elsewhere, but if you do not have power fold now (which I'm pretty sure you don't), you would need new mirrors, a door switch and modules for the door. Otherwise you can wire up the power fold option to a separate switch that's completely independent of the truck.
The only "issue" you will have (I'm having this same problem as I just swapped mirrors a month ago) - if you add tow mirrors, when you flip them up - the power adjustment buttons will be off by 90 degrees in the direction you flipped them. Basically, the truck does not know it has tow mirrors on it, so it's not looking for the sensor that indicates what position the mirror is in.
All of these features can be flashed to the truck by the dealer, as long as your truck had ability to be ordered with the option. I don't believe you could order your truck with power fold mirrors to begin with, so they wouldn't be able to flash that code for you. But you could get tow mirrors, so they would be able to put that one in if you wanted down the road