What is the lowest quality of video that can be provided as a proof?

How can I speedrun on a weak pc? My PC: graphics - AMD Radeon 6670 CPU - AMD Athlon(tm) 64 x2 Dual Core Processor 5200+ 2.7 GHz RAM - 4 Gb I am speedrunning Hollow Knight and my pc can not stably output 30 fps with OBS studio and livesplit

I have very old PC and my OBS automaticaly choosed low-quality video. How i can set obs to normal quality and normal fps?