Hi @Madalyn_Destafney , this is a genuinely under-documented area, so I'll share what I can and flag where it's worth confirming directly with support since mixed-storage behavior is still maturing.
On the sandbox refresh question: a sandbox refresh copies from Production, so the refreshed environment reflects Production's state at the time of the refresh, including storage configuration. So if you convert a portfolio to cloud storage in SB01 for testing and later refresh that sandbox from Production, that testing change would be overwritten by whatever Production has it doesn't "roll back" in the rollback sense, it's simply replaced by the Production copy. Worth noting that Preview refreshes automatically while a Custom Refresh Sandbox only copies from Production when you manually schedule a refresh, so Preview being in one state doesn't necessarily mean your other sandbox lanes match.
On environment promotion and storage type: this is the one I'd most want you to validate directly, because the "no rollback" rule for cloud storage (once an object is on cloud storage, it can't go back to legacy) intersects with promotion in ways that aren't clearly documented. The safest assumption is that promotion carries the object's configuration, but I wouldn't want to state definitively how a cloud-storage object promotes into a Production context that may be in a different storage state without support confirming it against your specific setup.
On Group-level storage enablement affecting promotion: I'm not aware of documentation confirming whether the promoting user's Group membership affects env promo when storage is enabled for specific Groups rather than the entire org. This feels like an edge case that hasn't been formally documented, so I'd flag it specifically to support.
Given how specific and consequential these are for your rollout planning, I'd strongly recommend raising all three with your Adobe account team or a support case in parallel with community input ,mixed-storage promotion/refresh behavior is new enough that you'll want authoritative answers before relying on it. If you do get confirmation, it'd be hugely valuable to share back here.
