don't purchase games on the dummy account, use your main for that. the dummy is for the gamepass/xbox live sub after your main accounts sub expires and you wanna hit that new members lick.
and yes, whatever account has purchased games/subs/etc, as long as its set for home xbox, any account that logs into that xbox can access the games.
example: if I showed up to your house and logged my account into you xbox, id be able to play all your games(purchased and gamepass downloads) on my account and use your xbox live privileges.
