I’ve been lucky with the OB 100 SD. It seems to fit my face well enough with the available adjustments.
The single tubes are good but certainly not at the level of the best telescopes I have looked through. In use, I can see a little bit of flaring around the brightest objects if I look through a single tube. Some of this (but not all) is my own aging eyes and obviously it is substantially reduced in binocular vision (where the neural processing cancels out idiosyncracies from each eye). However, not all of it is my eyes but none of the problems are what I would call objectionable in the uses I put the BT to.
A pair of Nagler 5mms gets me to 112x, a pair of Tak 4mm TOEs gets me to 140 and a pair of Nagler 3.5s gets me to 160. I also have the OB 22 mm, 14mm and 7mm on hand yielding 25x, 40x and 80x. Just for context, I am usually able to merge images in most normal binoculars fairly easily (at least, easier than some friends of mine manage). Have also spent most of my life engaged in various visual pursuits (painting, photography etc.), so I’m reasonably sensitive to visual issues. I have no trouble with merging images at lower magnifications and almost none even at 112x. I can merge images at 140x and 160x but need to be more conscious about head placement. If not, I’m likely to see double images (some of this is idiosyncracies in my eyes - I know because when I slide the object from the right visual field to the left, the images merge into one). I also have to be careful about keeping the eyepieces properly aligned in the collets - I generally try to get the holder vertical when placing eyepieces, I find it easier to keep everything square that way. However, that means I cannot do the usual start with low magnification, center object and swap out for high power eyepieces dance. On the upside, it has made my dead reckoning and star hopping skills better.
I will say that high powered binocular viewing, with its challenges, can be a pretty charming experience. I can happily spend an entire night wandering around the moon. Even at the high powers mentioned, it is still more dimensional in binocular vision rather than monocular vision. Twin 100mms are reasonably potent for deep sky in the skies I observe from.
To your point, I never use it in telescope (one tube only) mode. The binocular mode helps cancel out some of my eye’s problems and the view through one tube at high magnification is not as fine as using one of my telescopes. Sort of have to accept the instrument-observer (me) combination for what it is and what it is best placed to do.