Ended up fixing this the roundabout way.
I started out making a back up, so definitely do that.
Some useful info from this post.
All of the files within the main project config folder will repopulate with defaults, which in most cases doesn’t require a file at all so most won’t appear unless you poke settings again. The DefaultEngine.ini file in particular holds the settings for MobileHDR and other rendering features which were causing the crashes. I was able to delete out entire chunks of this file (again, make backups) to determine that the Project Settings/Rendering section was where the problem was. I wasn’t able to partially delete within this section, so I couldn’t test deeper.
To fix the problem, I deleted the DefaultEngine.ini file, loaded my project, switched back to the SM5 preview mode, and then closed the project. Finally, I copied my original DefaultEngine.ini file back into the configs folder, overwriting the new one, and reloaded the project.
Knowing how to recover the project, I was able to mess with the settings a little bit to be able to use the feature without crashing. Ended up disabling Mobile Multi-View.