Hi. How do I access an iPhone backup stored on my Windows 10 PC, without restoring it to an iPhone?

What I have used is iPhone Backup Extractor (iphonebackupextractor.com). It is very good, but also pretty expensive except for the free trial. Two features that I find useful is it can extract from an encrypted backup (if you know the encryption key) and also iCloud backups. There are some free ones; here is a list that includes some free ones→https://www.imobie.com/support/top-best-iphone-backup-extractor.htm

Another option of you are pretty handy with software is a SQLite viewer, as the backup is a SQLite database.

The only way to transfer the contents of a backup to an iOS device is by restoring the backup. You cannot selectively access files and settings in the backup. It is all or nothing.

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Edit - I have no experience or knowledge about using third party software to extract files from a backup, so I defer to Lawrence Finch on this matter.

If it is an encrypted backup, you can’t. Otherwise you will need either a SQLite browser or a 3rd party iPhone backup extractor app.