Avskum
Hi,
The CLI Installer has the possibility to select the default shell. Calamares has for this no implementation and can be only set in its config.
You could set it in /etc/calamares/modules/user.conf to your preferred shell. It does default to fish.
You can also just change after the installation your default shell with chsh /usr/$SHELL
What do you mean with “more light version” ? You can simply select or untick the packages you want in the online installation.