Now I downloaded the manual for the Z 50 - have it the way you wanted! 
So, you push a button and then select an ISO value on the X-T30. At some place in this long list will wait the AutoISO settings.
On Z 50 you push the ISO button and turn on or off Auto ISO with the front dial or select (and override at the same time, if AutoISO is active) the ISO value with the rear dial. I fail to see a big difference? Especially the override bit is new to me, I can't do that on Z 7/6
On rare occasions I DON'T use AutoISO, such as studio works, architecture and landscape - everywhere else AutoISO is active as I do not care much about noise but do care about aperture and shutter speed. Noise is hardly an element of composition, at least in most pictures - the other parameters are.
And the way my two Fujis are set up with ISO values is different from what you describe. In the Q-menu it's only the top value of AutoISO, not the low limit. In the menu there's a list of ISO values and three entries AutoISO▸ and after another click I can see the values but not as an overview.
Again, why 3 AutoISO (to set up and remember) but no U1..3? I admit it's time consuming to set up these banks and User settings - but after it's done, it's a time saver, especially since the banks can be named. U1..3 is as difficult to remember (which settings are for what) as AutoISO 1...3 - and within the Z series, one cannot export them and import it to another Z camera - it has to be the same type.
So, you push a button and then select an ISO value on the X-T30. At some place in this long list will wait the AutoISO settings.
On Z 50 you push the ISO button and turn on or off Auto ISO with the front dial or select (and override at the same time, if AutoISO is active) the ISO value with the rear dial. I fail to see a big difference? Especially the override bit is new to me, I can't do that on Z 7/6
On rare occasions I DON'T use AutoISO, such as studio works, architecture and landscape - everywhere else AutoISO is active as I do not care much about noise but do care about aperture and shutter speed. Noise is hardly an element of composition, at least in most pictures - the other parameters are.
And the way my two Fujis are set up with ISO values is different from what you describe. In the Q-menu it's only the top value of AutoISO, not the low limit. In the menu there's a list of ISO values and three entries AutoISO▸ and after another click I can see the values but not as an overview.
Again, why 3 AutoISO (to set up and remember) but no U1..3? I admit it's time consuming to set up these banks and User settings - but after it's done, it's a time saver, especially since the banks can be named. U1..3 is as difficult to remember (which settings are for what) as AutoISO 1...3 - and within the Z series, one cannot export them and import it to another Z camera - it has to be the same type.