I'm fairly certain that you can disable the word processor, as well as a lot of the other "core" features. Or at least I'm seeing a whole lot of "disable" buttons when I look at the list of active apps for my Nextcloud install.
Yes, but they are still part of the package. If you have only 500MB you easily run out of disk space for both the installer and the actual installation. And I think they remain on your disk, ready to enable. There is no easy way to remove them completely.
In the AIO you have to explicitly choose to install them, in the bare metal setup they are not installed unless you choose so when you install for the first time. You're right that Nextcloud has gotten bigger, but Collabora is in no way a default part that you can't uninstall...
