Well, there are few ways I've heard and read about.
The one is obviously getting two cams connected.
Another way is splitter,yeah. Lot's of them tbh nowadays, the most popular are splitcam, visit-x, verysoft, manycam. Among them only splitcam is free and will be good that way but it takes about 30% +- of your CPU. The others are not an option in free versions but they are much better than a splitcam if you buy the whole package, no CPU overloading and a good quality provided. With any of that you would be able to provide HD for two sites easily. Though I'm not sure if OBS can use the image of splitter cause I'm not using any, but OBS definitely doesn't want to see the image from logi capture for example so I'm afraid the same story occurs with any splitter.
And about the OBS. You can just run one more OBS window for another site. Also notice to download a virtual cam plugin for OBS. So you select your cam as a source in one of them and in the second one there will be able a virtual cam. Btw there are lots of OBS versions and I'm almost sure that the one provided by the Streamlabs will be not that 'heavy' for you CPU.
Though any of the above will require a good PC, thanks god nowadays it's not a problem usually.
But if any issues occur you can try using so-called cloud streaming. It doesn't need anything speacial but the good internet. A bit new stuff for now but I've heard of few.
