Starting config. for 2019 iMac SSD upgrade: Fusion or SSD?

[fmnamado]

Hello, I also have an iMac 19,1 with 1TB fusion drive (1TB HDD plus ssd blade I think is 24GB).
I want to replace the SSD blade with a SSD and "destroy" the fusion drive.
I want to keep the 1TB HDD for files and new SSD, possibly also 1TB, in the M.2 blade, without fusion drive.

Do I have to do something when installing the operative system so it doesn't try to build a fusion drive again?
Can I keep the other operative system in the HDD, if I need to boot to get something there, or when I rip the SSD of the fusion will I loose the data?
I would want it just temporarily, just in case I need.
In the future I would also wipe the HDD.

Can i remove the SSD blade and keep the Mac OS working as it is, without this cache?

Thank you for your help in advance.

 

[DeltaMac]

The SSD is an integral part of the fusion drive, not just a cache. The macOS system in a fusion drive "lives" on the SSD, for example, to take advantage of the SSD's speed.
So, removing the blade SSD "breaks" the fusion drive. You can't boot just from the hard drive, unless you have added a system partition, and installed macOS on the hard drive, which is basically what you would need to do.
If you want to separate the SSD and the HDD, you can do that, but that then means that you must reinstall the macOS system on the HDD (and you get to put up with the slow speed of a modern macOS on a spinning hard drive