Which system version for MBP 2011?

Hey, I know there is lot of similar or same questions. But Im still not sure about it. I have MacBook Pro 2011 early (non metal) with 16 gb ram. Im planning to upgrade with new SSD, battery and add new cooling paste. After that I would like to give him to my wife for some simple work (documents, tables, mails) with little bit fun (youtube, Netflix, social networks). Which version is best option? Cause I think about Big Sur and Ventura