Epson V500 - Image Type? Target Size? You'll see I'm confused!

[slowdive]

If anyone has an Epson V500, I could really do with some advice.

In Pro mode, in the 'Destination' section, there's the following:-

'Image Type' / 'Resolution' / 'Target Size' / 'Scale'

I have a few Agfa Scala films that I'd like to scan in and possibly print up to 20" times 16". I also have some standard colour slides that I'd ideally blow up to the same.

Would I use 'Image Type' - 16bit Grayscale (Scala) and the highest resolution I can get?. The software goes up to 12800dpi.
Or are B & W slides scanned in using '48 bit colour' with high resolution?.

Also what is the relationship of target size and scaling?. The range for Target size goes from 'Original' to 'A3'.

If someone could just tell me what I'd use for each one of the following I'd be grateful

1) Image Type
2) Resolution
3) Target Size
4) Scale​