None of the above.
I also do backpacking and while I'm not a ultralight, (and not interested to be), you know that weight is extremely important. Many peoples has gone with an 8x32 (mid-size) because, while a bit heavier, the comfort is much better than compact. But for backpacking weight is too much important to get anything but compact.
I will go for the Bushnell Custom 7x26 for many reasons. I have these binoculars and they are, IMO one of the few acceptabes compact binoculars. You have to understand that compact binoculars are streching the specs to the extreme limits. The reason peoples are buying a lot of cheap 10x21 is because they know nothing in binos and they are not well informed. If you want compact, you definately have to go mid-price, specially if you want something light.
Many things influence the amount of light transmitted to the eye. The ratio of the size of the lens over the magnification (exit pupil) is important. Also the quality of the glasses that will transmit a certain % of light and the lenses coating that will reduce light reflexion. In full light anything will do. But in the forest, you are mainly in a mid-light environment. This is why, for the mid-priced binos, I consider the 7x26 the be the extreme minimum. Otherwise, you have to increase the lenses diameter if above 7X or go with high price products.
The Bushnell H2O, I was selling these to peoples who was interested in the cheap 8x20 at 17$. The later are pure crap and I'm not a "anything below Swarovski is crap" type of person, not at all. But just for the weight the h2o binos are a tight heavy for backpacking IMO.
As for the Custom not being waterproof, don't worry. Mine are over 15 years and they've literally taken a beating and had to adjust the optics once. You don't use binoculars when it's raining and just leave them on your backpack when it rains. Anyway, while not waterproof, they can take a few drops no problems they are not fragile at all, belive me.
IMO, the least you should do before making the move is learn more about the very basics of binos. Example, learn what are the implication of the ratio of the lens diameter over the magnification (exit pupil). You will understand why peoples are trying to send you in a different direction.
Feel free to ask more questions.