My novels (so far) have ensemble casts, so I use third person omni POV throughout. Typically, while still conforming to rules to avoid head-hopping, I'll allow up to three POVs within a scene. But only one is the primary POV, which might include "contemplative" thought. Others, I only show having "reactive" thoughts–expressions of surprise, shock, disbelief, rejection, etc. ("What?" "Oh, shit!" "Impossible!" "No! Not while I'm around!" ). These latter I use in italics.

Your comments on backstory possibly interfering with Deep POV were interesting. I really struggled with including the backstory on two of my characters in my second book. A big part of my problem, though, was that while I needed to provide them with deep, compelling motives for their actions and allegiances, I also needed to withhold their real identities secret until the climax.

The result is that I had two chapters (one for each–a dream sequence and a flashback) that pop up unexpectedly, without any clear connection to the rest of the story events, but which readers know (because they are vivid, emotional childhood crises) must have some significance. In honesty, my hope is that readers just scratch their head, know these must have some significance, and then let them slip their memory until just before I introduce the "big reveal."

I don't think I'd classify my novels as being Deep POV, only that I have occasional elements of deep POV mixed in. If that's considered a thing....

Glad it was helpful.

Absolutely. Going deep all the time is exhausting for writer and reader. Not every scene is served by deep POV. Sometime you just open a door, go to work, or fly across the country.

The same questions still apply. Not every internal
Threat involves physical danger. If they’re rock climbing, is there any past experience intruding on the present? What’s at stake? Whether the climbing is part of the plot, or a device to facilitate struggle or even conversation, what’s at risk? Fear of failure? Identity - what if they slip in front of someone or they don’t have the right brand on their gear or there’s a stain on their pants? To a perfectionist a stain could be identity threatening. Does that make sense?

Great! Glad to hear it.

Awesome. I have tended to lean heavily on crit partners because I'm too close to it for emotional arc edits.