MPI at a minimum, and potentially a LPFP depending on how hard you push the turbo from my research.
E mixing is only useful if you don't have a flex tune, and mainly used to bump up octane or solve knock issues on pump tunes. Normally mixing upward of E30 is fine on most tunes and stock hardware. Though you can get a tune for a specific E blend, like an E-50 blend, or such.
Hardware otherwise depends on tune and and such. You can either do an external gauge/BT module like Fuel-It or Innovate, no gauge with a direct flex sensor signal to the ECU and a ecu gauge reader, or a combo of both. Normally people use water testing kits when blending and a app or other Ethanol calculator to figure out how many gallons of pump and e85 based on Eth %. Really depends on what you plan on doing for your tune, as some of this can be specific to that your chosen tuner or platform for tuning.