Storage recommendation to transition from Windows to Mac?

I currently have a Windows 10 with 2 drives - one for apps and setup with 930 GB storage (I have used 335 GB) and the other for files etc with 465 Gb storage (I have used 457 GB). As all my other equipment is Apple, I want to swop to an iMac desktop. As most of these files contain important information or ones that contain happy memories, I am uncertain what storage I shall require on my iMac. I would be grateful for any comments.

Many thanks

William

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