I don’t believe there are plans for a start menu, it’s not how they envision the desktop. However anyone is welcome to cook their own, like this project.
I believe the team is focused on Flatpak. There’s a community project adding some AppImage functionality.
For feature requests you can search/raise issues on the COSMIC GitHub repositories.
Yes I encountered that when I used Tumbleweed on my laptop, the solution was to run "sudo prime-select boot offload". It set up my laptop to use iGPU for desktop environment and NV offload for gaming. I made it part of my update script. No idea why that wasn't handled better.
But generally I'm done with rolling distros, I now use an Ubuntu derivative that still keeps kernel and mesa quite up to date, I enjoy a stable environment.