How to Move Old Games to the Xbox Series X

Yes they were still on my old Xbox one but still no luck getting them moved to the x series

3. Unless you're doing a network transfer to move games over, you don't even need the old console to move to a new one.

This is going to sound stupid, but would the games come over anyway with the Xbox account via the Cloud on the Series X and/or adding the Series X to the devices on the Microsoft account. Or is a network transfer an alternative method?

The games on the SSD will run fine on it. You won't need to move them to the Xbox Series X storage to play them. Only the Xbox Series X games & games optimized for Series X will need to be played on the consoles own storage.

Because on my Xbox series x, it only shows 'Optimized for series x/s' but if a xbox series x version of a game is NOT 'optimized' how would i know if I'm playing a series x/s version of a game?

There's not a One X series. There is a One X and a Series X. A Series X (and Series S) are the newest consoles and what new games will be released for. Anything labelled as a One is old gen and studies are not releasing many games for those anymore.