let me know whether .tiff, .jpeg or Vuescan's 'raw' are the best? Also, any ideas on cleaning off dust on negs for scanning?
The VueScan Help pages have some advice on TIFF and JPEG:
Hints and tips
File Formats
I've used VueScan to get my Nikon CoolScan scans into Lightroom for many years. If you're archiving you'll want to use a lossless format like 48-bit TIFF with compression. If you want to have VueScan save at the highest quality levels, think about whether you should turn on some of the advanced features like multisampling, manual focus, and infrared cleaning to get the best possible quality out of the scan you're saving.
The VueScan "raw" format predates the digital camera raw format and is not the same. VueScan raw means no image adjustments have been applied at all, so it looks "wrong" if you open it because it isn't even white balanced or gamma corrected, and I don't think negatives are inverted. But unlike a digital camera raw file, VueScan raw is already an RGB TIFF. VueScan raw can be useful if you would rather make every adjustment in a program other than VueScan, but it really means editing from scratch.
I think it's better to have VueScan make some basic edits like white balance, black point, and white point, save as TIFF, and use Lightroom to refine them from there. I like to set the black point and white point a little wide to make sure they don't clip the original scan, then evaluate in Lightroom.
JPEG doesn't preserve all of the original data, but it might be OK for quick scans that don't need to be perfect, like party pictures or an image you're only going to email or post small on a web page.
To clean film, I use one of those blower brushes with a bulb on the end that I squeeze to blow air out. Some people use cans of compressed air. I keep a small clean brush around in case dust needs to be dislodged.