With 8 GB of RAM (in signature below), I believe one at a time is gonna be your best bet.
I've got a lot more memory in my machines (32 to 48 to 56GB), but I still do only one render at a time per one machine.
I don't think there is any benefit in rendering multiple scenes at the same time with one machine, but I suspect there might be a slowdown at least at some degree in the total rendering time for all of the the scenes combined. And your memory will be eaten for sure.
AC25, Rhino6/7+Grasshopper, TwinMotion • Mac Pro 6,1 E5-1650v2-3,5GHz/128GB/eGPU:6800XT/11.6.5 • HP Z4/Xeon W-2195/256GB/RX6800XT/W10ProWS