I think the GPU can be used for processing the final edit into a finished video file. It sounds like what you want to do is "scrub" through your video known as "scrubbing" and I think that is all processor and SSD power. If you are working with 4K or 1440p video then thats a lot of data to scrub through, especially the data rate on the SSD. An HDD is gonna hurt big time trying this. There are some video editors that use "proxy" files (small versions of your original footage) to enable faster scrubbing and thus require less processor/SSD performance.
Personally, I use VSDC
https://www.videosoftdev.com/ . The free version, totally fine for my needs of 1080p full HD content creation, but the paid version can utilise the video card for the final edit and enables a full set of enhanced special effects and gadgets.
Please detail what spec PC you are using, which might indicate the challenge and what resolution and FPS you are working with.
Please list full pc specs
CPU:
GPU:
Mobo:
Ram:
Ram configuration, slots, xmp (on/off) :
PSU:
Storage:
Windows version:
BIOS Version:
Monitor screen resolution refresh rate:
Run UserBenchMark and post a link to the results. It's helpful to the community to see how your system is performing against same spec rigs worldwide.