We just upgraded from 9.2p1 to 9.3p18 using the non NVE. We currently don't use that feature yet but if we do, could this be done by choosing the next version with NVE. We have the FAS2650 unit with dual controllers.
Yes, that's correct. When you upgrade a newer version you can select image with NVE. Going from Non-NVE to NVE should be fine, but going from NVE to Non-NVE could be an issue, there is a BUG:1012881 (But it is already Fixed in 9.2).
NVE is not supported if the command output displays the text 1Ono-DARE (for no Data At Rest Encryption), or if you are using a platform that is not listed in Support details. Also, it needs "AES-NI" capable processors applies to certain old and all newer platforms (FAS2650 is supported).
The following command determines whether NVE is supported on cluster.
cluster::> version -v NetApp Release 9.1.0: Tue May 10 19:30:23 UTC 2016 <1Ono-DARE>