The OnePage website evawilhelm.de is based on the static website generator HUGO and has two special features:
- The individual sections are managed in HUGO as page bundles. This allows a high flexibility in creating and maintaining the site.
- I have developed a kind of “low-tech CMS”, which allows the website owner to easily update individual sections of the website via the web browser.
(And before someone writes again: but that’s what Netlify is for: I enjoy simple solutions, like also the lowtechmagazine) 
Many smaller websites are rarely updated. Either because it is not necessary, or because the website owner does not find the time for it. I think it would make sense in some cases to create a static website and then, if perhaps in the course of the year a little something needs to be changed, to hire the agency.
However, there may be good reasons why this approach does not seem attractive. While most of the page may not need to be updated regularly, there is e.g. that one area where current dates are published, or a current notice text should optionally appear.
I have chosen the following strategy for this: I use HUGO as a static website generator. In addition, there is a kind of “low-tech CMS”, which ultimately consists of a single php file and gives the customer the possibility to exchange individual texts on the page itself.
All details about my implementation you can read in this blog article (in german)