There are MANY threads on this same basic issue
The 'fix' involves appropriate settings at Operating System, OBS Studio and game AND your coming to an adequate understanding of what running OBS Studio (or any similar software) involves.
Even a PC many times more powerful (workstation class machines) than what you have can be brought to their knees depending on Operating System settings, foreground (game) & background processes, and OBS Studio settings.... all of which need to be balanced with each other.
Some games work with certain approaches/settings, others don't. The exact driver setup you have, etc....
OBS Studio is a powerful, sophisticated application, meaning there is a level of expertise required to make good use of it... And as Operating System is a moving target, as are drivers, game code, etc... what works for one game/PC may not work on another, or a year later... nature of the technology... and OBS Studio is free, open-source, meaning you need to keep you expectations in line and the reality is you will need to invest the time to learn the technology, especially around the implications of
- native screen capture alternatives
- implications of CPU impactful plugins, filters & effects
- GPU impact of certain settings like Psycho visual and lookahead
- impact of screen refresh rate, OBS Studio FPS, and game FPS (especially why uneven multiples is a bad idea)
granted, what would be nice is some clean documentation of all of the above... but with no paid staff, an understandable desire but not a reasonable request. so up to you what your preferred educational approach is... mine was to follow these forums (for 4+ years now).. you could start by scanning thorough the forum for subject lines similar to yours and see the responses. and learn from that.
- start by not ignoring the pinned forum post on posting log with an issue (when asking for help)
- Beware clueless YouTuber's who post definitive 'how to' videos when they don't provide context as many times they are more clickbait content that only works (if at all) in a very limited scenarios.
- if you search for the easy button, you are likely to get frustrated and misled... the answer is typically multiple issues, with a lot of 'it depends' on your specific setup. Just be aware, you may simply need a minor tweak to OBS Studio, and you'll be all set; Or you may need to adjust some settings within your Operating System, and optimize for constrained resources; or change some settings in your game, and/or video driver especially game related settings [it is not uncommon for some game video output optimization settings conflict with video capture]. At the extreme, certain game setups and Recording/Streaming from some computer is just always going to be problematic, hence the 2 PC setup ... it depends
As you will see on LOTS of game threads regarding drop in FPS ... you can't max out a game using at/near 100% GPU, and a large amount of CPU, then add a computationally demanding workload like real-time video capture, and not expect somethign to 'give'. [well, you can, with certain GPUs but in a manner that almost no one wants... ]