Hi Miguel,
thank you so much for the (way too short 
) insight ! It indeed helped a lot understanding of the whole process.
That you’re only using clip gain in the first stage is some important info…i guess my mistake was to set fader levels right at the beginning (using a mix of the two). Sounds logical to have them at somewhat homogeneous gain before touching any fader.
then I’ll correct that minor loudness discrepancy or let Nuendo do it for me.
Let Nuendo do it - can you explain that further please ? (And can i tell Nuendo to do the whole mix for me somewhere ? 
)
choose loudness settings on Nuendo export menu.
Just checked, i can’t find any setings regarding the loudness there, can you explain that too, please ?
Another thing is room calibration - from what i’ve read, working at a fixed 85dB SPL is obligatory ? (never done that either for example)
About the master limiter - are there any plugins or hardware you can recommend for that ? I’m currently using the Flux/Jünger Level Magic (does something very nice to transients) and a hardware NTP 179 400 limiter (never clipping, adds some body, set before the Level Magic)…although i’m quite happy with this combo, i have no real comparison.
Also, speaking of mastering, i use to insert an EQ on the main groups except DX (especially on music) that takes out a few db in the vocal range for better clarity of the dialog…is this something common to do ? After all it’s probably a matter of taste, but i’m curious.
If anyone wants to share their favourite go-to EQ’s i’d also be interested to hear. I know there’s a gazillion of choices…just recently i discovered the Kilohearts Slice Eq and it’s such a breeze for quick DOP for example.
I highly recommend getting a control surface for that.
I would very much want to use one…does there any large enough exist for a budget of under 2K Euro ? I was thinking of getting a modified Mackie d8b, but these things are so old and probably unreliable. Although, for automation rides i’m still using an even older Radikal SAC 2, eight channels…yippieyay
Sorry for bothering with even more questions and thanks again