Toggling Account Groups visibility makes a few changes, but on the whole, you can include any accounts in a report, even if they are invisible.
The only instance visibility affects Report is when picking exact entities. If you only have a few accounts visible you will only be able to select those in the account drop down. Similarly, you will only be able to select campaigns/ad groups/ads from accounts that are visible in the entity selector. If you leave the selection on All Accounts, all accounts, even invisible ones will be added to the report.