In your previous device it could Mac / iPhone / iPad if iCloud photo library was always set up see the articles Set up and use iCloud Photos - Apple Support
Change preferences in Photos on Mac - Apple Support
System Photo Library overview for Photos on Mac - Apple Support
And all applications box were always turned as on including photos / mails ....Turn iCloud features on or off - Apple Support
The photos will sync in new Mac when it's set up Set up your MacBook Pro - Apple Support
The second method for transferring mails from one Mac to another Mac .
- Take back up of all mails in V 7 folder , is in Mac OS Catalina 10.15.7 and V8 folder is in Mac OS Big Sur
Click on finder take cursor on top menu bar > Go after that hold option key click on > library > select mail folder > right click on mail folder there itself > click on copy mail > right click on the desktop > click on paste item .
Entire mails are copied to V 7 folder and will get saved on the desktop .
Note : For Mac OS mojave the folder will be V6 , For Mac OS High Sierra the folder will be V5 , For Mac OS Sierra the folder will be V4 , For El Capitan - the folder will be V3 , and for OSX Yosemite the folder will be V2 .
Take a USB flash drive and copy V7 folder into it , once it is copied right click on the USB stick and eject it .
Insert the USB flash drive in the second machine .
Configure new IMAP account Add an email account to Mail on your Mac - Apple Support in another machine , go to top menu bar , file > import mail boxes > import data from > select apple mail > click on continue > select the back drop folder then choose new .
When new IMAP account is opened a new folder with all mails will appear in the mail side bar , you can rename the folder .