Best way to backup everything before flashing new ROM?

Hi everyone, so I was wondering what was the best way to backup everything, apps, apps' data and system settings before flashing a new ROM or the same but with new base (which usually requires a clean install).

I've been told that the TWRP backup isn't that great because it'll bring over the "junk" from the previous version, and it doesn't really backup photos for instance.

Samsung's SmartSwitch, at least for me, doesn't backup applications at all. I've tried the phone version as well as the computer one, the phone one crashes once it gets to the app part, the computer one finishes but then there are no apps backed up.

I tried Titanium Backup but I don't know exactly which is the best option, should I be backup just apps and data? Or system data as well? If the correct way is both and let's say that the new ROM is "more" debloated", wouldn't I be putting back in the bloatware by backing up system data as well?

As far as system is concerned I just want to backup something like alarms, memo, system settings like brightness and I think that's more or less it.

Thanks a lot to anyone that helps me, I've been making tons of backup recently trying to find the best solution but couldn't.