If you use VE PRO and you have multiple instance of one instrument, VE PRO will load the samples in memory only once
If you have different instruments it will load them depending of the size of the sample buffer you have define in Directory manager.
If your samples are on a HD you have to leave "standard" if they are on a raid of HD, on a ssd or on a raid of ssd you will be able to load less in memory
It is not recommended to use multiples VI in on song as it will use more CPU resources than using in a VE
Best
Cyril