Is it possible to increase IPhone 14 ProMax 128GB memory with ICloud ?

I guess that would depend on the way you use the phone. For me, it would be more than enough storage space, as I do not take a lot of photos or videos on the device. If I do use the phone for photography, any photos worth keeping would be copied to my home computer, then deleted from the phone. For users that never delete or move content from the phone, more storage would always be helpful.

No, it is not possible to add storage space to an iPhone.

The space required by an iOS update is minimal. The vast majority of space used on any device will be user content, such as music, videos, photos, apps.