1. Yes, you can run other generators while doing Sample Digitizer scan. 4.5 is noted to be more detailed.
2. We've run all of them with good results. My preference is now to run the shorter SD scans and GenX contact scans at least once a week. Every now and then I throw in a 4.5 hour SD scan as well. We use both Plasma and Remote to run the results.
For more details, please check this link: