Hi Becky,
everything matters. 😉
VE Pro 5 will always try to process audio from top to bottom - unless you tell it to do differently. 8-) I tried to cover most of the possible scenarios in the Tutorial sections of MIR Pro's manual, starting with p. 37. But I have to admit that some of the screenshots are out-dated due to the fact that VE Pro has developed quite a bit since 2012.
I'll try to summarize the most important points for you, therefore:
1. In most cases, MIR Pro will replace any panning-device in you processing chain. IOW: Any panner/balancer etc. will change (and most likely destroy) MIR Pro's output. The screenshot you posted shows some bypassed Stereo Panners; personally, I tend to remove them completely, to avoid any errors.
2. Any plug-in you use before MIR Pro will change just the signal you send into MIR; consequently, any plug-in you instatiate after MIR will also affect its output, thus the room and positioning. As a rule of thumb, all time-variant, non-linear and level-dependent processings like compression, modulation, delay effects, additional reverb, saturation etc. will produce different results when used pre- or post-MIR. EQ and filters (i.e. linear, time-invariant processing) on the other hand will give you more or less identical sound both pre- and post-MIR.
3a. VE Pro's 5 AUX-Sends can be set to derive their signal pre- or post-fader. (... right-click an AUX-send to switch it pre-fade - the fader-path will appear in orange now instead of the usual light-blue). Quite logically, a post-fade AUX will always receive its signal from "the bottom" of the channel ("after the fader"), so all plug-ins will have an audible effect. The position of the AUX-Send fader is irrelevant, in this case.
3b. BUT! 😊 As soon as you switch an AUX-send to pre-fade, its position within the channel does indeed make a difference! You can have (all) your pre-fade sends with or without the effect of certain plug-ins, depending wether you move the faders to a position before or after these insert slots. - As an example, you could send an uncompressed signal component into an effect-bus for some dynamic echoes, while you compress the signal afterwards, before it reaches MIR inside the same instrument channel.
... I hope these lines shed some light on the topic. 😊
Kind regards,