CMS for Humans And Machines

Ok, I have to find a suitable CMS what will serve as backbone for my newly developed PWA application and I have no idea which one to choose. Because of that I have decided to list my thought and maybe even get some suggestions from others. This post supposed to be as short as they can, so I will switch directly to the point. This is not an blog post with solution, it is more about the questions and my understanding what I expect from CMS. Also I hope it will be a series of blogposts where I will rise more question and at the end, at lease I hope those questions will lead to some answers and final solutions. Recently I and my team  have developed mobile PWA application. Project is almost done, some final design related updates will be added and the project will transition in maintenance stage. The current customer has his own CMS and a lot of content. Now I have to move this product forward and need to find some CMS for it. Also the same CMS should be suitable for new upcoming ...