Add alt+shift to change keyboards:

gsettings set org.gnome.desktop.wm.keybindings switch-input-source "['<Alt>Shift_L']"

This means there is no need for gnome-tweaks which has the problem of having to press alt+shift twice to get out of English (see link above).

Add Caps lock to change key, both shift to enable caps lock shift to disable it:

settings set org.gnome.desktop.input-sources xkb-options "['grp:caps_toggle', 'shift:both_capslock_cancel']"

You can instal gnome-tweaks, open dconf-editor and view what the options do.

How to have: Caps lock to change keyboard and turn the LED on! Then, shift caps to enable/disable caps lock.