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.

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.

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.