correct - I put my Pre+ to Airplane mode before switching to my Pixi+ and as soon as I turned WiFi back on, it called home to mama, saw I was logged into another device and wiped my Pre+. I had intended on switching back and forth between them but the reload time for apps and data was excrutiating, plus many Pre apps didn't work on the Pixi, so I switched the Pixi to another email address. When I went to my Pre2, i did use my original profile since I'd bought so many apps. I know the Pre+ will wipe when I turn it on someday, but that's OK.
so, decide if you have enough paid apps on the Pixi that you'll want to use on the Pre2 and can do without on the Pixi if you use it again. If so then you can create a new profile on the Pixi after it wipes itself. Otherwise a new email address for the Pre2.
I spent about the same for my off-contract Verizon Pre2 using my developer coupon and have no regrets at all! I do miss my Pixi keyboard thought
good luck and enjoy!
edit: i don't know about compatibility between profiles, which was probably the point of your question!