the control room

hello everyone,
i have nuendo 3.2.1 and found myself very very confused with the control room suddenly.
i have read all the documentation i could on the subject but there are still few things i can’t work out:
i can’t audition clips in the pool and when importing audio.
i just about managed to get the Click (metronome) somehow to output while playing.
i have an RME 96/52connected to an 8I/O convertors via ADAT optical cables.
outputs 1&2 of covertors go to a Mackie mixer and speakers.

the RME is a 3 ADAT+spdif card so provides 24 channels and spdif but my 8 I/O is connected to the 2nd one (i.e. 9-to16).
ch9 and ch10 (convertors outs 1&2) go to my Mackie so that’s what i chose in the Studio tab in VSTconections.
i haven’t assigned any main output because i don’t want the main mix to go anywhere.

i have tried different combinations but i’m still very confused.
anyone can help?

Many thanks,

Check your PM, Fabrice.