@champsupertramp, thank you so much for your prompt response. Exactly what I was looking for!
A few questions:
1) Is there a way to delete photos generated with now removed/unused sizes? I guess I can do a find/rm in the terminal.
2) I seem to have to pick a 2x photo size to avoid blurriness, even though I selected 100 for image quality. Is that expected?
3) I see the images are stored under wp-content/uploads/ultimatemember/<user-ID>/. I feel using an arbitrary directory name (or at least some kind of checksum) would have been more secure. Not a big deal but thought I would mention it. It does make it easier to find photos if I need to manually remove/change them.
Thank you ??