If I choose DISC then the box at the bottom says "no burner detected" though I do have NERO
Nero is a software program that lets you burn to dvd it does not interact with Elements.
Have you looked if the driver of your burner is up to date?
I just made an dvd iso and burned it to DVD with CDburnerXP (is a perfectly safe program)
Its in dutch but you get the idea
Can you please check whether your DVD burner is there in Windows explorer or not?
If Premiere Elements does not detect your burner then you can use ISO 4.7GB option to create ISO image and later you can burn ISO image to disc using Nero or any other third party software.
Premiere Elements 14 came out defective for burning DVDs. Premiere 13 works perfectly fine, burns DVDs and uploads to YouTube without any problems.
NERO does not interact with Premiere Elements 14.
Adobe should correct this deficiency with a software update.