You do not state how loaded your 5 Orion modules are, but I am taking it you got the 16 core 24GB recommendation from the Multi Module sizing guide.
The beauty of VM is the ability to adjust resource assignment easily and therefore you can tune the specification based on actual usage. I suggest to our customers that they determine the ease at which resources can be added and if difficult will size higher, to allow them to reclaim resources once they have a baseline. If it is easy, then I will use my experience to get the appropriate size and ensure the customer is prepared to add more resource if it turns out necessary.
Regarding the dedicated NIC, this really depends on other VM's configured on the host. We are talking about monitoring and therefore it is important the measurements being processed are not affected by anything. Therefore the use of a dedicated NIC keeps the communication clean on the host level.
I hope this helps.
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