Sideloading or preinstalling?

Sideloading already existed, but only for ostree flatpaks. Flatpak also supports OCI flatpaks, but the support for those aren’t as good, hence the previously missing side loading support.

I hope the performance significantly improves by then. Beta 1 felt pretty rough to me. And also, animations.

The security and privacy don’t matter much when most of the emails you get are coming from unprivate servers like Gmail or outlook.

The main reason I hear is that it maximizes screen usage and helps avoid/limit the tediousness of having to manage windows.

Not what you’re asking for, but I’ll give you my perspective as someone who’s tried tiling on and off and overall don’t like it.

1. Applications work best at certain aspect ratios, having them automatically tiled to different aspect ratios can be annoying
2. Some windows windows/pop-ups have no business being tiled. Like some Yes/No dialogs (not all windows specify a max size which would avoid triggering the tiling) or a simple calculator. And you can specify which ones to have floating, but it requires setup.
3. Sometimes it ends of causing more work than floating environements. Most of the time I only have a max of 2 windows open, but occasionally I’ll quickly try to do something then end up with 4-5 windows, at which point that’s too many windows and I need to reorganize stuff to continue working. But that usually wouldn’t be an issue in a floating environment.
4. Worst of all, just setting up a tiling environment is a nightmare. You have to configure the actual compositor/WM, which tools you want to use with it (bar, launcher, screenshot tool, notifications, screenlocker, etc) and configure all those too, ideally with some basic theming to make them look coherent. But inevitably you end up with missing functionality especially in the modern area where an app might be sandboxed or expecting all xdg-portals to be implemented, which most compositors don’t do.

Cosmic is exciting in this regard since it aims to be a fully-featured floating and tiling environment. You could just toggle between them as necessary (or have them on separate workplaces). You also get much better portal support.

Maybe Secureblue?

That also comes with its own hardened browser based on GrapheneOS’s.

And if you don’t go with Secureblue and its browser, I’d recommend using a browser Chromium based, probably Brave. I know that’s a controversial choice, but in terms of security and ad blocking, it’s one of the better options. And disable JIT for V8.