Hey there,
Your specs are on the weak side for streaming. In terms of settings, that's hard to say. I'd start with the lowest settings for obs and see what your output video is like. It's prob gonna be very choppy even at a low gaming/output res of 720p/30fps.
You really need a good 6 core CPU and a higher tier GPU for a better experience and that's like the min. For effective streaming with good 1080p/60 output, you'd ideally want an 8 core CPU with a recent mid tier GPU like a 2060S/RTX3060/Ti/Radeon 5700xt/6600xt. Your system as is, is only good enough for low-to med settings for current games, and that's without any streaming being involved.