My website is not very large – about 10 pages and 130 posts (per language version). But it’s growing about 1 post per week.

Might just leave it as it is, without any multilang support, apart from a choice in the top-right corner that takes you to the alt. language website version. Google searches in each language show the relevant language page version, so it seems to have figured it out without the hreflang. With good page rankings as well – so probably no double content penalties (languages differ vastly, only images are the same).

I’m not selling anything so this seems like too much bother with questionable benefits to the visitors and the google as well.

Considering adding hreflang codes manually on home pages, and a few top-landing pages perhaps, but not sure how exactly to do it or if it has any downsides (like plugins do, in terms of slower website, problems when/if uninstalling them etc.).