https://nataliekraneiss.com/ (@natalie@hcommons.social) I agree with your concerns about not being “able to edit or delete the syndicated posts afterwards”.
In short, my personal site tantek.com is its own “instance” but without running Mastodon.
I use https://fed.brid.gy/ to connect my site directly to #fediverse sites like Mastodon servers, without any need for syndication, cross-posting, or publishing copies of my posts. More details here: https://tantek.com/2022/301/t1/twittermigration-bridgyfed-mastodon-indieweb
Because I use my site directly, I can edit/update/delete posts, and send a Webmention to #BridgyFed to propagate those changes to any #fediverse servers caching my post, all of which update themselves accordingly.
I’m not that familiar with the WordPress ActivityPub plugin, however, there’s a great community of folks who can help with any questions about it here: https://chat.indieweb.org/wordpress
Hope that helps and good luck!