If you have a decent nvidia gpu, you should use Nvidia Shadowplay. It has a very low overhead.AverMedia Game Capture HD 2 sounds good for you. I personally use Elgato HD60 as I prefer 1080p60fps. I think AverMedia Game Capture HD 2 captures up to 1080p30fps or 1080i60fps.
This is a surveillance camera. OP was looking for a way to capture his screen without performance decrease.Hello.
This one is wireless but also LAN and USB and has 720p/60fps:
https://www.amazon.de/Überwachungskamera-Überwachung-Schwenkbar-Sicherheitskamera-Zweiwege-Audio/dp/B075ZRK9N9/ref=sr_1_10?__mk_de_DE=ÅMÅŽÕÑ&keywords=pc+screen+capture+device&qid=1555664497&s=gateway&sr=8-10
A little cheaper then the capture devices.
Is there any sort of hardware you can connect to your pc to record your screen
Yes. He means capture cards. Not cameras.I understand this in that way.