Rebuilding a website without losing SEO when you have very little SEO to begin with

My website rebuilding project has been in the works for a few weeks now, and I’m very happy with the direction the new site is going. However, I’ve reached the point where I’m almost ready to make the switch from my old site to my rebuilt site, and I want to make sure I don’t make Google mad at me.

A little background: My old website is on the domain booksbyjayna.com and is built with a clunky free builder that came with my small hosting provider. The new website is built with Divi on WordPress, hosted at DreamHost. It is currently living on jaynabaas.com but will be transferred to booksbyjayna.com after I’ve deleted my old site. All my new pages are drafts right now, and I’ve checked the box to discourage search engine indexing so Google doesn’t get confused by duplicate content. None of my old pages are getting much traffic. Even the ones that have slightly better traffic are not optimized for SEO, and I expect my rankings to get better all the way around once I’ve switched to my new, better-optimized site.

So my question is, how careful do I really need to be about matching up all the URLS and carefully redirecting everything?

I’ve read some articles that say I need to do site crawls and audits and Google Search Console and all that good stuff, and other articles say I probably don’t need to worry about it that much. I’m especially unsure what to do about my blog posts—I have maybe two years’ worth of non-optimized book reviews on my old blog, at whatever random URLs my site builder assigned outside my control. As I optimize and repost my reviews, the URLs aren’t going to match (and I don’t really want them to; they’re ugly). I also have a short story from a different genre that I plan to drop from my new website, which means that old URL won’t have a match on the new site either. Do I need to redirect all of those old URLs? Or do I just figure my traffic can only go up from here and it’s not really worth the trouble?

I’m very ready to just get this move done, since my new site looks so much better than the old one. But I don’t want to inadvertently call down the wrath of Google. Any techy types care to give me advice? Thanks!