Depends on what apps you are actually using. Most apps can automatically sync to your Google account, so that will back up your data.
eg contacts or calendar or Chrome can do this. Or Google Photos, though it may not store the full resolution (but good enough for most phone cameras).
I only have a few apps that need to be backed up manually. One of them is K9 Mail - if you have multiple accounts, its very handy to backup the settings for them all. Other apps are Work Log and Trainspotter, which are perhaps more niche...
Or any mapping apps, worth backing up any waypoints or tracks that you want to keep.
I'm not bothered about SMS, most messages are transient anyway. And good to have a clear-out every so often. If a particular message is worth keeping, I'd take a copy elsewhere (eg Google Keep).
I think its easiest to create a folder for backups on Google Drive, then copy the important files there. Then you can easily restore it on a new phone.