> 2. Lazy loading: I am not sure if Chrome has it or not but FF doesn't load a tab content until I switch to it.

This is usually transparent to me. Except when I am on a train and realize that all the tabs I have opened in the background have never been loaded. :(

For this and other reasons I have removed tabs from my workflow, now I use 90% maximized or half-screen windows. It is also easier to alt-tab between them.

You can simply uncheck "Don’t load tabs until selected" in the General section of Preferences.

I don't know how people can live without Tab Groups. Usually I am working an 5 to 10 different "projects" and for each project I have a tab group with everything from 3 to more than 20 open tabs. Based on the project I am working on I can just switch to the correct set of tabs.

I could do something similar with bookmarks but that would be way slower and not as comfortable.

I do this manually (in FF) with one window per project, and N tabs per window. Works well enough even without extensions.

How do you do the per-window-stuff? Do you use a different firefox profile for each window? And how is it handled if one window is closed?

In this setup you just have to be careful to quit FF rather than close a specific window.

There is a Chrome extension called FooTab that does #2. Maybe Chrome will add this functionality at some point. I have heard that they are working on unloading tabs when many are opened at once.