The Bltouch link above does not include a cable compatible for the ender 6. The ender 6 uses a different connector on it's breakout board so you'll have to splice using the kit above to make your own.

Or you could use this kit (not mine) which includes the right cable, the mounts are built into the Ender-6 hot end housing already, I'm using this one and it works great.

As for the Pi, you can use a 2GB kit with octoprint, but I'd recommend using a 4GB kit since it's relatively cheap, will be slightly faster and will future proof it.

There's some extra components you can use to hardwire to your ender-6 PSU (which I'm doing). If that's something you're comfortable with doing and know how to do some electronics work I can send you the link for my step-downs etc I used to hook it up.