Recommended SSD Size on new 24" iMac

I agree with the other comments about buying the biggest you can afford.

However by using optimised iCloud storage there is less need for huge internal storage capacity.

As an example, when I upgraded last year to the M1 24” from a Mac Pro desktop with almost unlimited upgradability I decided on 512GB. I reviewed my apps and only installed those which I actually needed and any files which were for long term storage were put onto external usb drives. Optimised iCloud storage was enabled.

After nearly a year in use my M1 iMac is using less than 60GB out of 512GB and as I’m using iCloud my photos etc are also accessible on my iPhone & iPad.

The fallback solution to needing a bigger internal disk in the future is to boot from an external USB SSD of whatever size suits.

Impossible question to answer as EVERYONE has different needs. Buy the highest capacity you can afford and ensure it is at least the same capacity as your last Mac. Also, please remember you can always add external storage to augment the iMacs internal storage.

Everyone has different needs but take the highest capacity you can afford because you cannot upgrade the internal storage later

The largest you can afford.