I think this mostly depends on your own personal preferences and what services you're using already. For simple things, I generally use AirDrop to move between my personal iMac and iPhone. For Numbers files, I'll use iCloud. For other things I need stored on my NAS, I'll use the Files application on my phone and an SMB share on my computer to manage files.
For work, we use Sharepoint and OneDrive, so I use OneDrive on my work MacBook Pro and iPhone to keep files in sync and accessible between those devices. This, or another similar service, such as Dropbox or iCloud Drive, is what I'd recommend to most people who need to access a large number of files that are synced between their devices.