My best tip is don't use Ubuntu especially the latest version they're in the middle of a full kernel rewrite and it's chaotic bad.

I would say the following:

• Encrypt with a strong password 3+ word (your password manager should help you with this) for FDE
• for admin account (root), if there is a way to disable it in the setup configuration menu, disable it. Its recommended to use sudo when you need elevated perms rather than su root.
• backup all your files to an external drive, you can use rsync,rclone sync, or other items to do this. FreefileSync as well.
• before you switch over, run a flatpak list --columns=application to output all the flatpaks you have installed. This way you dont have to try to remember what you had installed
• Gnome software center is a bit slow and laggy, at least my experience on Pop! and Debian. I would recommend just using cli for apt installs and/or dpkg installs.

For the flatpak output, i would recommend the following script to help download all automatically:

flatpak_packages=(
	com.calibre_ebook.calibre
        all flatpaks listed here
)

flatpak_install(){
	for i in "${flatpak_packages[@]}"
	do
		echo "Installing $i"
		flatpak install --user flathub "$i" -y
	done
}

This will go through each flatpak and install it for you, saying yes to all so you don't have to do anything. Don't forget to run:

sudo apt install flatpak -y
flatpak remote-add --if-not-exists --user flathub https://flathub.org/repo/flathub.flatpakrepo

That's my brain dump at the moment lol. Lmk if you have any questions.

Keep a list of any packages you install for your hardware, just in case you need to reinstall down the road

As long as you have a strong backup strategy, I would recommend full disk encryption during installation, especially if for a laptop. Peace of mind with negligible cost on modern hardware. Even accessing the encrypted disk from a live USB takes only two extra commands compared to an unencrypted disk. As long as the LUKS header doesn't corrupt, hence the need for good backups.