Xbox Series X slowdown when downloading games

Not really...

Xbox Series X games / upgrades / updates has to be installed onto the Series X internal or expansion card SSD,

You can have Xbox One games on your external hard drive that will get an Series X upgrade but the games will need to be transferred to the Series X and then the Series X upgrade will need to be downloaded onto the Series X SSD,

As an example...

I have Marvel Avengers on my external hard drive that will get the Series X upgrade and I will transfer the game over to the Series X SSD ready to download and update the game to the Series X version when available.

I was under the understanding that when you download an Xbox series x game it has different code, so it wouldn't be possible on xbox one x. Which would also be the same for the hard drive. The xbox series x game is apparently different than the same game
for the series x.

I have the Xbox one X project Scorpio, I was told that the game can be downloaded in any serie X or serie S (included mine), thanks for the help!!

Game can only be downloaded on a Series S and Series X, but not an Xbox One X. Xbox One X is not the same as a Series X.

Ok I have both versions of GTA downloaded on my series x the Xbox one version works fine on the series x I then downloaded the series s/x version on the series x I then launched the game and it gives the error message

when you said series did you mean Xbox series type and

if Xbox series s/x has cross play option for mw2 it's it possible from to download mw2 on Xbox series s if

it has cross play on this game.