I understand your thinking why would anyone want to stream to Instagram Live and Twitch while playing PC games?
I say it is an easy place to pick up followers and if they want to watch in better quality add a link straight to your Twitch or preferred streaming website
2 OBS instances, 2 aspects ratios, 2 different scenes, 1 gameplay stream, 1 pc
P.s I know it's YouTube in the screenshot was testing on private account