Another question... How do I tell it to download and install the 64 bit version? Say if I did this with Gimp (about to try.) Also, how to run updates on individual apps, or do I just run it for everything?
UPDATE:
So I figured out I could check the versions of an app that are available with:
apt-cache madison gimp
Substitute gimp for whatever you want to check. After doing that I type:
sudo apt install gimp
That installs it. To upgrade it I type:
sudo apt upgrade gimp
It may seem daunting or even scary to use the terminal. But it really is the easiest way to manage software (installs, removals and upgrades). Now anything you install with the apt command will be updated every time you perform:
sudo apt update
To get the latest repository offerings and:
sudo apt upgrade
To actually download and install updates within that version (focal).
.deb and .tar.gz files will need to be downloaded almost every time you need to update them. This is a good reason to attempt to find a ppa/repository for most of the software you want to use.