I wonder if the performance and battery issues that some people have been having and others have not can be explained in part by different chipsets and/or modems and iOS having to deal with both: https://www.repeaterstore.com/blogs/main/for-better-cell-sig...

That article mentions that the iPhone 7 was the first one to have both Intel (non-CDMA) and Qualcomm (CDMA) versions.