You mention wanting to add flow to your collection and nothing will do this better then the shadow. No pops and a seven shot combo, it just doesn't get any better.
If you add pins to your collection by committee ie with and kids then rfm will be the ring loud by the vox populi but if you have sovereignty and your primary concern is game play then the shadow is the go'er.
Shadow is a tough tough player and the wizard mode is even tougher. Rfm not so much but it does have humour going for it and being one of two does that diversity to a stable.
Expect sanctum wear when buying shadow and possibly go the nu core on rfm depending on how long you keep your planks.