Hello Asaad
Until now VSL-Libraries have been recorded mainly dry so that we all are able to put them into the room we want. A disadvantage is that you need to do this work anyway otherwise it sounds not as we are used to.
Now you have several possibilities.
A) The easiest way is to use MIRx. If you are using the presets which are given for the most instruments Panning and the position in the depth of the room is made for you - fix, more or less. I personally would use those presets with a bit a lower wet-amount than they are originally offered by VSL. The results are quite good.
B) A great helper as well is the big brother of MIRx: MIR Pro. It is as easy as well to use it because you only have to put your instruments some where on the stage either the way we are used to or in your own style. Beside this feature (placing the instruments on the stage wher ever you want) you are able to choose much more: Microfone positions in the room, stereo setup of the microfones and you have built in effects for changing all the acoustic wishes you have... Advantage: There quite no limits Disadvantage: As often with such tools, their strengths are often the weakness as well. All the adjustable parameters you also can bring far away from "good"...
C) You can do the mix in the "old fashion way" with a panner, a convolution reverb and an EQ. Then you need to make the following tasks: 1) Draw a stage with the positions of your instruments on a paper (Example) 2) Decide how many different depth you like and open for each depth a group-Track (sum) in your Daw. 3) Insert a Convolutionreverb in each Grouptrack. 4) Try several IRs and choose one which can let the instruments sound as far a way as possible (100% wet). Now you can set the distance by balancing the dry/wet-balance. (One of your questions) So you are able to install 4 acoustic distances with 4 Group-Tracks. D) Route then the closest instruments through the closest acoustic distance and so on. 5) The farther away instruments sound the more their highest frequencies are damped. This effect can be simulated with an EQ in each "Distance-Track".
D) A total realistic sound (how we are used to with real recordings) you get with samples with the integrated room sound. This is what VSL will offer us with the coming up Synchron-Stage-Samples-Series. With this samples we will - hopefully - have nothing mor to do with panning, giving depth etc. All those things will be done. But here as well: the force of those samples will also be the their weakness: We only will have those synchron-stage-sound.
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Keep in mind that C) - even if it seems not to be very difficult - needs a lot of experiences for having nice results it is an art so to say to get good mixes, because the instruments from close to far need to have the correct volume EQ-settings etc. Because you do not have any limitation here you can reach super mixes but also very bad ones (the strength is the weakness). The SUITE-Effects do not come with template presets so far (as I know). But they have a lot of presets for any instrument for leting it sound in an other way (more powerfull, more harsh, more distant, more clear,...).
Further: Keep in mind: Sibelius is OK for setting the score but if you are interested in a maximum of reality concerning the selection of the "correct" articulations, using x-velocity and using all the other controllers you should move your project into a daw (answers to your qustions). As a first fact for this advice: It starts with the setting of the volumes of tones: Sibelius does not offer 127 different signs for reaching all 127 midi-volume-steps. within a daw - no problem: Watch this short video
Mixes with A) or B) are more or less very easy to do because MIR(x) mixes for you. And if you not choose a too much wet ratioo the results can sound quit good. Music with A) and B) tends to sound often a bit equal over the time. You can fight against this "matter" by using different venues.
Example A) & B): French_Parade.mp3 (Guy Bacos)
Example C): It shall show what I mean with "no limitations" concerning the venues, depths, effects etc. within the same mix.
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I hope that my post could show all the different possibilities and that you can make the decission which way you want to go now. A) & B) are shorter C) can be very long and if you want to wait a bit you can choose D) and your mixing-problems are probably completely solved 😉 Also Sibelius and eventually a DAW was a question...
All the best
Beat