The number of "items running in background" after Mac OS updates has increased substantially. My primary question is can they be trusted or should I disable each and every time?

You installed them. You should have asked the "trust" question when you chose to install the software that runs processes in the background. They have always run in the background. Ventura now tells you that they are running.

Are you talking about the applications in:  > System Settings > General > Login Items > Allow in Background?

I only have Adobe Acrobat Reader DC and OSMessageTracer that run in the background. Nothing was added after Ventura update for me.

If you are concerned about the amount of processes running in Activity Monitor, there is no need to worry. You could stop them, but they would just start up again.

Apps like EtreCheck is a free and highly recommended app in this community that is used for diagnostic purposes and will show you the apps that are running on startup. I would urge you to remove any antivirus or cleaner apps that show up in this report.