Merging site A and site B into a new site, site C -- help with redirects

Hi everyone,

I’ve been running two sites, site A and site B. I now want to combine them on a larger site to encompass both areas, a new domain as site C.

I’ve redirected every individual page on A and B to the new page published on site C, but should I also redirect the homepages to the new site, or leave them as is?

Additionally, though I’ve redirected the posts from sites A and B to site C, they’re still live on the sites, they just auto-redirect. Should I now delete these posts on the site, or leave them there but with the redirect in place?

And is there anything else you recommend I do to most effectively communicate to Google that this new site is where indexing of the original content should be?