GTR V1.0 BIGTREETECH direct connection with Pi and Octo

Working on a new printer with GTR V1.0 BIGTREETECH and M5 board. Would like to connect Pi and GTR directly, so here´s my questions:

Did anyone already use this combination? What´s your experiences in it?

Which pins to connect at least? Don´t wanna block the full range of Pi pins.

What port or other settings to be done in Octoprint to make use of this connection in stead of standard USB-Port?

What did you already try to solve it?

Additional information about your setup (OctoPrint version, OctoPi version, printer, firmware, what kind of hardware precisely, ...)