First of all, what version of WordPress are you on? Gutenberg is slowly becoming the editor for WordPress (although there is still the classic editor option). There are (with every plugin or instance of any software) different evaluations. Gutenberg is like Marmite as they say here, you either like it or you don’t at all. I am not doctrinaire. There are things that it does very well in a manner I am not sure about. So let’s leave that aside.
It sounds as though you want different layouts depending on content. This is easily done using a child theme (there are plugins to set a child theme up) and different page templates. Once you have set up your child theme, you then have to make new template pages. One for your “project A” content, another for “project B” and so on. These templates can be very radically different to each other, or not, depending on your design decisions.
There is plenty of help out there to create these template pages (unfortunately I don’t have any links in mind — google might be your friend here). Creating new template pages is something I have done — it is not hard, but does require some time and patience, both for design decisions and their implementation.
I hope that helps you on your way.