From my understanding peertube has less restrictions of content compared with youtube. But I could very well be wrong. I'd say upload content to both. It won't hurt having 2 types of audience and could potentially bring more views. I know several creators that upload to both.

In my experience everyone has to start somewhere. I started with just a simple headset mic and eventually got a Blue Yeti usb mic. You don't necessarily need a powerful pc. Programs like OBS, especially if you are just recording, can be optimized for lower end PC's. I recorded on an old laptop for a while and it worked just fine. Start with what you have and upgrade when you can. Good luck!