Hi Gukas,
by mistake, I just deleted a nicely worded, lengthy reply I wrote to your inquiry (it's simply too hot in Vienna these days ... the ridiculous 35 to 38°C take their toll ... 😛 …). I'll try to keep it short now. *sigh*
MIR Pro is meant to be used as virtual orchestral hall (or studio), set up readily for a (virtual) recording session. It will take care for all aspects of spatialisation, which encompass panning, positional information, reflections and reverb. I wouldn't make a rule out of it, but for starters*) this means that you can leave out all devices you would usually need to achieve these acoustic impressions (i.e. panners, reverb engines, delays etc.).
But much like in case of a “real” recording session this doesn't mean that the hall will “magically” fulfil all your artistic and/or aesthetic wishes! Keep in mind that you are now in the position of some kind of “omnipotent” conductor. 😉 You are the “ears” of all musicians on stage, so you will have to take care to balance their interplay which they would otherwise take care for themselves. Technically this means that at some point you might want to employ additional processing like compressors, harmonic enhancers and (most notably) filters and EQs – both to the individual instruments as well as the actual mix you achieve with MIR Pro.
MIR Pro tries to lend you a hand in doing so: The so-called “Character Presets” give quick access to a collection of tailor-made “colours” for most Vienna Instrument.
… I compiled more hints like that in a dedicated section of MIR Pro's manual, called “Getting 'that' sound”, on p.55 ff.
*) Once you are more familiar with MIR Pro and it's possibilities, you will of course encounter situations where some these processors might come handy again.
Hope that helps!
Kind regards,