2 Accounts Signed in on same series x, both will open the same game

Make 1 of the Xboxes the "Home Xbox". When done make sure privacy and sharing preferences are set on the "Home Xbox" to share. After that all the games on the "Home Xbox" are accessible by any profile added to that "Home Xbox. The other (non "Home Xbox) has to have the game purchased under that 2nd Xboxes main profile or purchased as a gift from any profile and sent to a chosen profile to be downloaded when that profile signs onto their Xbox. I have an Xbox One X in my living room controlled by my 2nd account profile. I have a Series X in my game room "Home Xbox" controlled by my 1st profile. Example; I log on the Series X with that main profile and buy/download Division 2 with all expansions and passes. I then log on the One X with my 2nd profile (main for that One X) and buy/download Division 2 with out the expansion and passes. So now a family member adds their profile to the One X, if they own the Division 2 they can play it and as much of the content that I have purchased. To play the full version on the One X someone has to buy it for that console, However anyone else that logs onto the One X with their profile that doesn't own any of Division 2 content can't play it at all. They can launch it but it will direct them to the store. Now adding Ultimate Game Pass to the One X allows profiles to download and play any games available through game pass. Remember my Series X will allow any profile added and signed onto can play any games and use the Ultimate Game Pass to download and play from my Series X. One X has limitations for profiles due to that profile owners games owned and which games are in the One X. Confusing ........ ?

You need to assign one of the Xboxes as both of your home Xboxes. This will allow you to share games without the master account being signed in

https://support.xbox.com/en-CA/help/hardware-network/console/my-home-xbox

It's 1 of the Xboxes that are "designated" "Home Xbox" not the profile, though the profile that set it up should be the "main profile" for it. That means email and passwords and Microsoft account that controls the "Home Xbox".

both Xbox one and series x should be the same account and therefore won't make any difference, unless you have 2 separate, if 2 separate accounts then you are out of luck.

The subscription can be used on any Xbox One or Series S/X that you sign into. As long as you're using the same account on both consoles, you'll have access to the subscription.