I'm trying to picture what you mean in 2. I suppose you mean monophonic ie., single line MIDI tracks in Logic going to a multimbral instrument in VEP.
Personally on the VEP end I don't find a multitimbral Kontakt, .nkm saves on resources enough to become a mode of operation for me. I do it occasionally when it's a family/from the same library and the reason for that is to compare in the one window the different mic'ing, decca tree, etc ambience setup. EG: Spitfire, Orchestral Tools interface.
Kontakt runs into an incompatibility in VEP when it gets into the 'Unassigned' outputs which are its 32 monos, (default setup 16 pairs but this is now 2 channels in the host, not one) so the functional use of a multi ends at Stereo 10, anyway.
No Vienna Instrument is real multimbral, ie., while an instance may use 4 stereo outs there is a single channel possibility only.
I write almost exclusively in monophonic lines; as to writing chords in a single track, I don't see a problem with, or a necessity of, a multitimbral instrument. If you can assign channel per note you can make a single MIDI track talk to the individual members of a multi independently, or same w. multiple single instances (via the same 'Omni/All' VEP channel matching sequencer assignment).
I write multiple single lines inside one 'Omni/All' track in Cubase frequently, but Cubase has MPE support as well as Note Expression* (*for instance one note in the part may have a different CC1 or CC11 et al curve than another), and full MPE requires "All".