Whichever way you do the upgrade,?please?backup your data before performing the upgrade. ?It is a major leap forward from macOS High Sierra 10.13 to macOS Ventura 13. ?Your system drive will automatically be reformatted as AFPS, with two (2) volumes, system and data (introduced in macOS 10.15 Catalina). ?Due to Apple's bidirectional firm links, the two volumes appear as one in Finder, but show separately in Disk Utility. ?
I don't use iCloud because I have a lot of data and it's a subscription service. ?So I always do two (2) separate backups: a clone and Time Machine. ?Another possibility is a cloud backup service such as Backblaze (I've never used them, I've only heard them mentioned). ?That's probably also a subscription.
Given the amount of data you have, you could make a clone on a 256 GB USB flash drive, as they are very inexpensive theses days. ?Randy always recommends SuperDuper, which is free to use without some of its bells and whistles that are probably unnecessary in this scenario.
Whichever way you do the backups, verify that you can recover data from them before doing the upgrade.
Erasing your disk is part of a clean upgrade, so it is a bit more involved than doing an upgrade in place. ?A fully clean upgrade would also include a new installation of any apps that don't come with macOS. ?Because of that, you would need to restore all data from backup and reset all of your system and app preferences/settings. ?I used my 2010 MacBook Pro for 10 years and never did a clean upgrade, all with no problems. ?Other folks always do clean upgrades, because they think that clean upgrades can prevent some kinds of problems.
Just a few of the other changes you'll see (far from complete):
Mojave:
... Grab replaced by Screenshot app.
... New apps introduced: News, Stocks, Voice Memos and Home.
Catalina:
...?32-bit apps not supported.?
... iTunes was replaced by separate Music, Podcasts, TV and Books apps, in line with iOS. iOS device management is now conducted via Finder.
... Find My Mac and Find My Friends are merged into an application called Find My.
... in Terminal, Z shell (executable "zsh") is the default login shell for new users.
Big Sur:
... New Time Machine backup destinations are formatted as APFS.
... New Shortcuts app.
...?Live Text, which allows a user to copy, paste, translate and look up text from images (something that I use almost every day).
...?New Passwords Manager
... Visual Look Up makes it easy to identify objects (e.g. cat breeds, dog breeds, etc.) found within user's photos.
Ventura:
... Stage Manager?keeps the app you¡¯re working with front and center, and your desktop clutter-free (personally don't like it, but maybe I just didn't use it enough)
... New apps Clock, Freeform, and Weather?
... System Preferences was renamed to System Settings and got a new tabbed interface. ?It was re-organized based on the iOS/iPadOS Settings app.
Brent