So, here is an update on my questions.
Think I found why the 2TB drive was plotting so slow. It is a "fancy" Toshiba drive with "Powersave mode". If the drive is not used for a while, it shuts off, hence, the plotter needs to keep re-running the access to the drive.
-- Resolution: plotting and mining at the same time :). I started the plotter (AIO) on the 2TB drive using 3 of my 4 cores and then started the miner. Since the miner detects 2 plots, keeps trying to access the plot on the 2TB drive. It gets an error, but the access to the drive keeps it alive, and then continues to mine with the 3TB drive. Plotting fine and I expect to have it done in 3 days.
Now, I just need to figure out how to mine correctly with a Linux headless server...
Thanks all!