Many of your i-Pilot performance questions, particularly those relating to the Spot Lock and Track Record features, are addressed by the test data on my website:

Introduction to MinnKota's i-Pilot

Regarding some of your other questions:

The trolling motor must be deployed to record a track. Deploying the motor (I'm talking specifically about Terrova) powers the i-Pilot GPS receiver, which is necessary to record a track. I'm not sure how PowerDrive V2 motors work in this capacity, but it's clear to me that the i-Pilot was designed with Terrova in mind.

Slowest speed to record? As slow as you'd like, I imagine. To replay a track: you'll need enough speed to combat any wind/waves/current in order to stay on the recorded track. Track record only follows a path; the user can set their own speed during recording and playback, and change that speed as much as they like.

There is still an autopilot feature, as well as an advanced (GPS-based) autopilot feature. Yes....that's right...two independent autopilots that are user selectable.