Selection of Sentinel 1 scenes for DEM generation

Hello dear forum members,
I have pairs of Sentinel 1 SLC scenes covering my study area, some pairs have almost 100% overlap while others have about 10-20% overlap. Is there a guideline on the minimum percentage overlap required for pairing scenes for DEM generation? Secondly, is it okay to use two scenes with 100% overlap?


please have a look here: S1A-S1B coherence of partially overlapping images

As it is discussed there, as long as the images belong to the same track, you can use them for interferometry. Of course, only the overlapping area can be used to create the interferogram. But as long as the perpendicular baseline is fine (you can check using the InSAR Stack Overview tool), there is nothing wrong with products shifted along track.