I'd say shift to switch between mode is pretty intuitive, at least that is what I defaulted my game to. then everything else can be bound to space, that being the jump, wall jump and dash. (dash is only available in dark mode so it shouldn't overlap with double jump)
Obviously it would be perfect if you had key rebinding and controller support but just having one button for switch mode and dash and wall/double jump on the jump button would make a huge difference alone.
As for the wall jump, I noticed that you have to wait for the slide but sometimes I still got a double jump instead. Maybe I was pressing the opposite direction to early or I wasn't close enough to the wall and was pressing walljump without entering slide state.
Whatever it was I think that having to wait a second to enter sliding feels a bit weird. I assume you can only enter wall sliding state from falling and that may be the issue but I could be fully off base here.