Those are totally valid points about counter-play with the box enemies. They can get a little oppressive if you don't entirely know where they're supposed to be. Allowing space to jump over some of tighter ones could definitely help smooth that out.
The jump frames are something I played with quite a bit but I think you've got a solid point there. I wanted jumps to be considered vs twitchy but I think there's probably an argument that I could remove the lead-up animation entirely and the game wouldn't be the worse for it. I think the solution in the end might be a slight animation speed up and the implementation of a ghost jump buffer.
Thank you for the feedback! I don't mind the specificity, It's what I'm looking for in this project.