Learning to design and/or code for web today, I´d probably start here:
https://www.freecodecamp.org and here:
https://developer.mozilla.org/en-US/docs/Web.
Since the abandoning of Atom Editor, I´d grab a trial of
https://www.sublimetext.com or use another code editor like
https://vscodium.com,
https://pulsar-edit.dev or
https://zed.dev and simply start designing and coding with plain HTML and CSS. Later add SASS, JavaScript, PHP, MySQL and what else makes sense for you.
For experimenting with various web development concepts on a local Mac, I´d install
https://www.mamp.info (great for many different kinds of static and dynamic sites),
https://ampps.com (get WordPress and much more up and running with a click of a button). As a more advanced user, you might also want to install
https://www.vagrantup.com (set up the same environment like your client´s web hosting provider) and
https://www.docker.com (containerize to keep your system clean, while using many different services and tools for full-stack development).
Personally I don´t like Wix, but if you think it´s worth a trial, just go for it. Read a
comparison with WordPress to get an idea of what you can expect.
If you don´t like to code, but use some WYSIWYG editor, ask Apple why they were stopping iWeb development and then take a look at
https://blocsapp.com or WordPress plus Gutenberg, Divi or Elementor.
For many small websites you won´t need much more than a frontend UI framework like
https://getbootstrap.com and some basic skills of PHP to send a contact form. For some more complex sites, a static site generator like Jekyll or Hugo might be sufficient, too. If you need to set up a large scale dynamic project, you might end up with React, Angular or Vue plus a quite complex toolset to get things done.
For the design
https://www.sketch.com, Adobe Photoshop, Adobe Illustrator, Serif Affinity Photo, Serif Affinity Designer, Gimp or Inkscape might work for you, but with some coding skills, you can create just the visual content with those apps and then put everything together straight forward with your tools of choice.
As a final thought, it really depends on the project, what´s the route to go and what you should learn. There are endless ways to go… Start somewhere, choose to learn what looks interesting enough and what seems manageable for you. It should make some fun to have fast progress.