Should i alway rate at the same iso in the shadows - in direct sun and flat light - to make different pictures fit to one harmonic series?
Depends what sort of meter you use and what results you're hunting for. If you run a proper spotmeter then measure from the shadows and rate it to the box speed of ASA400, if using averaging- or even camera's matrix- metering then I rate the film to ASA250 or thereabouts, incident meter: ASA320 does fairly good for me.
On colors and contrasts: it all comes down to
inversion technique. Many softwares using automatic functions do NOT invert your negatives well enough - don't wast your time to straight invert function. Sometimes they may hit the nail when you have a very bright, dark and natural gray represented on the frame, so automatic adjustments can lock the settings around those once you auto-level and auto-color it after direct-invert, but it's rare to have it all well-balanced.
Hence
inverting smartly is the way to go - when inverted "right", then everything else becomes less problematic later on. Many people say good words about Color Perfect plugin for inversion, I'm using my own simple curves recipe for inversion that doesn't require any special software - any image editor with curve functions can do it. It's important to scan negatives as positives and linear (flat TIF), 16bit scans (with no adjustments at all, even white- or black points must be left alone) are highly recommended since you'll lose a lot of depth during inversion so 8-bit scan files can get very restrictive in tonal quality. I've created a set of my own unique curves for each emulsion I can recall as default starting points and customize in case the shooting condition vary (i.e. indoors, outdoors, contrasty, long exposure shots etc when the curves shift).
Some Pro400 examples in different light:
1,
2,
3,
4,
5. Most of them spotmetered from the shadows.
Hope this helps,
Margus