I use the Temporary Containers you mentioned, and find it to work very well. A couple of tips:

• I use standard (named) containers for sites I frequently visit, so that I don’t need to log in every time. You can set a website to always open in a certain container.
• For the browser restart problem, I just manually middle-click to open the tabs I want from my previous session, which opens them in a fresh temporary container. Indeed the old container state is gone, but I don’t really find it to be a problem.