@Darrylglenn I have chosen to standardise on 1TB plot files, however there is no hard and fast rule.
Back when I got started plotting and optimising were separate processes and I was using 4TB & then 5TB Drives so this made it easy to plot on one drive and optimise to another.
These Days using xplotter you can do the process in one go. Start with some smaller plots to ensure you have everything sorted then I would not go below 1TB but feel free to just fill the Drive with a single plot.
There is almost no difference in the scan speed for 5 x 1TB v 1 x 5TB plot.
Rich