This computer isn’t going to be great for streaming. But you can get some results from it
Start with the auto tuning wizard in the tools menu.
If editing settings manually I suggest you aim for 720p x 30fps 1500kbps bitrate and close every single app / program down before launching OBS that the computer doesn’t need to run.
i imagine one or two cameras might be okay but adding a third and fourth is going to stress this computer out and give you a stutter
You are likely to want to upgrade this computer. If I were you I would suggest something with an Nvidia NVENC encoder like an old 2012 thinkpad w540 with nvdia k1100m
if you have a bigger budget or want to game from the same machine you need something much more highly spec’d
my recommendation is based on the idea that you are not gaming from the same machine handling the stream
good luck!