I’ve actually built Resgen[0] to help tailor resumes to job descriptions. It’s been a boon for my own job search, getting me a lot more call backs. I plan to build it out to a whole personal recruiter that sources and applies to jobs for me.
As for sites, LinkedIn and Otta are the two that I’ve had the most results from.
I've used chatgpt to improve both my resume and cover letter. It takes a decent amount of finesse to dial it in but it's very much worth the time and effort. That's about it for me. I monitor about 10 different job sites, along with several other subreddits, slack teams, and discord servers
As for sites, LinkedIn and Otta are the two that I’ve had the most results from.
[0] https://resgen.app