All right, I've ordered and received my Solar Red U11! I'm being super careful with it, as the case I ordered hasn't arrived yet. I've downloaded and installed all the system updates, bringing the phone up to Oreo. A wonderful experience compared to my AT&T version of Note 4.
Now my question is: I've put in a new MicroSD card in the phone, and the phone recognizes it and everything. I was originally thinking of formatting it using the phone to be safe, but it warns that doing so makes the card only usable in the phone. Can anyone comment on whether this is true? And whether I should format it, or just leave it be? Thanks to everyone who chimed in!