So some inquiries that have bugged me about LrC Photo Merge HDR.
1. When I use DxO NIK HDR Efex Pro, I can select a reference image for deghoast, the reference image is used to nail down what frame that a moving objects is in wins out when the software needs to account for them. Example, moving boat. So, does LrC use the most selected image for this? I do not think so.
2. Just what resources does Merge Photo use? Camera RAW of course, what else? Paging file in Windows? Temp file? other virtual memory, RAM, what should be large enough, quick enough, for best performance during Merge.
Photo Merge in Lightroom Classic does not allow you to pick a reference image. Lightroom seems to use the 'best' image (the one that gives the least noise). Merge to HDR Pro in Photoshop (not the one in Camera Raw!) does allow picking an image for deghosting.