My system specs are:
9700k 8 core 3.6ghz
32GB ram
rtx 2080 super, 8GB
1070 ti, 8GB
If you want to be able to use your system while rendering, you need either 2 graphic cards or you need to attach your monitor to your cpu internal gpu (if it has one).
The locking up is coming from to the gpu that is on 100% load.
Rule of thumb for system memory: at least 2 times the gpu memory.
4 cpu cores are enough for rendering, but your system might feel slow while render is running.
So I better not try to render
6300 6 core 3,5ghz
8GB ram
RTX 650 , 1GB