Anyone tried ffmpeg vs HandBrake for video to GIFs? Or vice versa?

Site URL: https://the-movementexplorer.com/blog/2020/12/25/25-work-from-home-laptop-ideas-to-help-your-back-body

For the sake of page load speed, I've been reading about ffmpeg & Handbrake. Anyone prefer one vs the other? 

I'm Trying To:

• convert original .mp4s --> .gifs  OR
• convert .gifs --> .mp4s --> embed onto SS Blog Posts via either YouTube/Vimeo
• reduce file size to under 500KB (per file) if possible 
• retain some semblance of color & image quality (that's close to the original)
• upload a kabajillion "gifs" aka .mp4 animated videos to my SS Blog (i know - that page load time is gonna be crazy if these files aren't reduced in size)

Any suggestions or feedback about your experience with ffmpeg or Handbrake? Thanks!