Steve is in the process of digitizing everything and backing it up. Now he needs to consider backup options. Leo says the first thing he should do is make sure his data is encrypted. Windows 10 Pro offers BitLocker, which uses full disk encryption that unencrypts when he logs into his Windows account. He should be careful not to lose his password or certificates. He should back those up and keep them in a safe place.
For backup, it's difficult to recover lost encrypted data, as disk recovery applications tend to fail. So adopting a 3-2-1 backup strategy is essential: Three backups, two different formats, one off site. He should make sure the backup system is also encrypted, especially the one that's off site. One way to do off site is use network attached storage, then have a duplicate NAS off site to sync up with. Leo recommends Synology for that. It's not cheap, though, so if he's on a budget, Carbonite is a good secure option. He could also look into iCloud from Apple or DropBox. Steve should remember that off site backup services have the keys to his data and will give them to government upon request.
(Disclaimer: Carbonite is a sponsor)