Yeah, that’s a big, weird if though. Most modern apps can rely on the runtimes for their dependencies and not have to ship their own custom dependencies.
It’s different from something like AppImage, where everything is bundled (or Snap, where a lot more needs to be bundled than a typical Flatpak, but not as much as with an AppImage).
Additionally, there’s always some level of sandboxing in Flatpaks (and Snap packages) and none at all for RPMs, Debs, or AppImages.
Also, Flatpak dedupicates common files shared across flatpak apps and runtimes, so there isn’t “bloat” like what you’re talking about.
https://blogs.gnome.org/wjjt/2021/11/24/on-flatpak-disk-usage-and-deduplication/
Yep, ArcMenu (@ https://gitlab.com/arcmenu/ArcMenu which is the maintained one, last updated days ago instead of years ago) has a ton of different layouts which can mimic any version of Windows, and so much more.
When using GNOME, use the “Extensions Manager” app (from Flathub) to search for “ArcMenu” and install it, then you can configure it there in the Extensions Manager app as well. In the ArcMenu configuration, go to layouts and select the modern group to see something like the screenshot above. (The previews are generic wireframe sketches; the result will look much more high fidelity.)