Auto-updating mirror sites? RSS?

I would like clone one site to various URLs. For example, https://www.mastersite.com would have copies at https://www.clonesite1.com, https://www.clonesite2.com etc. Ideally, these copies should be slightly different to improve SEO, I guess. Somebody suggested pulling most of the content in using RSS. Is that worth looking at? Is there a plugin or some way to make creating and updating the clones easy and centralised?

Solutions described in terms that Homer Simpson would understand would be best as I’m no WP techie wizard ??