Well you're welcome to try it I can give you some settings but I doubt the results will be very good. I was gaming just fine on my old rig as well but when I tried to game and record it maxed the CPU. Are you using OBS or OBS Studio? If still running stock OBS I'd update to OBS studio they've made some efficiency improvements that may help. I'll list the tab to click and then I'll go down and list the settings.
Output Tab==> Recording
File Path- File path that you want your recorded videos to end up in
Recording Format- mp4
Audio Track- Only leave the check in box 1 and 2 leave the rest blank. If not recording your voice only game audio only box 1
Encoder- NVENC H.264
Rescale output- leave blank
Rate Control- CBR
Bitrate- 5000
Preset- Default
Profile- High
The rest can stay as is.
Video Tab
Base Resolution- Your monitors native resolution
Output Resolution- 1280x720 only use this if playing the game at a higher resolution
Downscale Filter- Lanczos
FPS- 30
Advanced Tab
Process priority- Normal switching it to high may help in your case as this gives OBS CPU priority
Renderer- Direct3D 11
Color Format- NV12
YUV Color Space- 709
YUV Color Range- Partial
Leave the rest to whatever they're set at. Those setting are the ones I used on my old CPU.
https://www.youtube.com/channel/UCSU89qv41sBmYN3pdYIW6wg is my YouTube channel I use those same settings except I record in 1080p 60FPS at a bitrate of 15000 (which takes a beefy CPU). I hope this helps and hey I could be wrong if I am post the video back in here and lets see the results