The main issues to watch out for are driver issues related to certain peripherals like fingerprint scanners, SD card readers, and certain oddball wifi chipsets. Hybrid graphics with both integrated CPU graphics and a dedicated GPU can lead to poor battery life in some systems such as many gaming laptops. In my experience, Linux runs fine on every laptop which I have tried it with, including 2 with hybrid Nvidia graphics. I’m also 2 for 2 on SD card readers and 3/3 on wifi cards as well, despite no prior research on my part.
Arch Linux sounds like it would be the closest to what you are describing. Or try out one of the more preconfigured versions like Endeavour OS or Arcolinux, as the install process for Arch can be a bit involved for someone new to Linux.
Usually not difficult so long as something is not a hard dependency for some other piece of software. Running something as root in Linux is as simple as typing “sudo” before a command and entering your root password
No. Per the above, elevated user privileges are permitted as a normal part of using Linux and do not require you to hack or bypass the OS’s security mechanisms like in Android or iOS.
If you install more than one, depending on your login manager it is usually as simple as a dropdown menu to select which DE you want to use when logging in.
Wayland is a window manager/GUI system used in Linux. It has been getting a lot of discussion lately because the Linux community is gradually shifting from the longstanding but now unmaintained X11 system to Wayland. You probably don’t need to worry about it.