If you have two or more different resolution videos in your sequence you will have to probably scale one or the other to match their resolution. You can do no matter their original resolution, be it 1080p, 720p or 4k videos.

In this video tutorial I will show you how to scale up or down this videos to have a nice continuity between them by using the Effects tab in Adobe Premiere.

OnePlus 5 Jelly Scrolling Effect: Confirmed
I think a recall is in order on the OnePlus 5