Best emulator for multiple instances of 1 app?

Basically i would like to run multiple instances of an app on 1 computer, its actually a small app and isn't a game or anything CPU intensive. the only way i can think to do this is by using emulators but many of them only allow you to run 1 instance at 1 time which means i can only run 1 instance of the app.

I have tried bluestacks and you can only run 1 instance of that at any one time.

Installed VM, Android Studio and Genymotion together which resulted in actually letting me run multiple instances of an android emulator at one time but if i load anymore than 2 emulators it just crashes and i get an error saying "display drivers has just recovered from an error". which i assume might be down to my graphics card or the drivers, i've updated to the latest drivers and its not actually a bad card so it should be able to cope with more than 2 instances.

any recommendations would be much appreciated. thanks

two bricked gs3s in one day, where did I mess up in both instances?

i think i bricked two old s3s today waiting on the little usb to come from ebay to see if i can fix them
first brick bootloader by accident to pda instead of bootloader
the second worked well from the older baseband to the mj2 to the mjb to ne4 rom without a reboot loaded, and when i did a reset it shut off and didn't come back on.

Where did I mess up in both instances?