I really doubt it. Pacman packages generally don’t have dependency version constraints so if you will pull some Arch (or Manjaro unstable) package to your stable system you will run into library compatibility issues.
I would say for bleeding edge just try unstable branch. It still stable enough (well Arch users use it and don’t complain about instability all the time).
There is also a way to use (the most bleeding edge) -git packages from AUR and compile it yourself against Manjaro stable libs but it will lead to recompiling every time lib updates.
You cannot - and should not - mix Arch and Manjaro repositories.
Running Manjaro on the entry branch named ‘unstable’ is mostly identical to Arch stable - with the exception of kernels, kernel modules, nvidia drivers and utils and of course the Manjaro exclusive packages like mhwd and other utils.
Also there is a couple of other Arch specific packages which are excluded due to incompatibility because they are very Arch specific.
You cannot mix stable and unstable branch - it will make your system prone to infesting of unspeakable horrors and general unstablilty.
Should you decide at some point to go all-in on Arch - it is incredibly simple to convert Manjaro to pure Arch.
The time taken to convert is 15-30 minutes depending on your system. I keep my notes up-to-date by doing the exercise from time to time.