First of all no i do not see the virtual keyboard(unless i check show virtual keyboard)
I don't have any problems with the japanese keyboard.
ofc i have aosp keyboard as default that is my english physical keyboard.
i use ctrl+space in order to switch from AOSP english only keyboard to anysoftkeyboard hebrew only keyboard and vice versa.
there is no way to switch languages with the physical keyboard so i switch the entire keyboard.
i have no idea what shit+0 does.
and i don't have experimental features on
i use the normal languages and input menu of andorid.
just settings=>Language and Input
i have AOSP and anysoftkeyboard(on hebrew) enabled.
pinyin disabled.
BTW it doesn't matter on what language your AOSP keyboard is on. it will always write in english.