Will upgrading cause a problem with...

I have an iPhone 6 that can't get any more iOS updates due to its age/model. I have an iPad 5th gen that can. I also have a MacBook Pro mid 2012 that can update to Catalina. Because two of my devices can update and my phone can't, would there be issues with updating those that can from a syncing across platforms perspective or anything else? Should I anticipate any other problems with this? Thanks!