When you select Outlook - 2016/13/10/07 - Optimized for performance while configuring a backup profile, insync backs up all the attached PST files and also the unattached PST files present in the folders containing the attached PST files.

Hence when you restore, you see these three outlook folders:

If you are backing up emails from Outlook 2016, 2013, 2010, or 2007, inSync provides two options for backup:

The following table lists the differences between these two backup options.

This folder contains PST files. An Outlook Data File (.pst) contains your messages and other Outlook items and is saved on your computer. When you add an email account to Outlook, a local copy of your information is stored on your computer. This feature allows you to access your previously downloaded or synchronized email messages, calendar information, contacts, and tasks without an internet connection.
Certain types of accounts, such as POP accounts, store their information in Outlook Data Files (.pst files).

This folder contains the AutoComplete list. Outlook maintains the AutoComplete list, which is used by both the automatic name-checking feature and the automatic completion feature. The AutoComplete list, also known as the nickname cache, is generated automatically when you send email messages from Outlook. The list contains SMTP addresses, LegacyExchangeDN entries, and display names for people to whom you have sent mail previously.

This folder contains signature files.
Whenever you create a new signature in Outlook, Outlook creates several files and folders including the .htm file, the Rich Text version and the plain text version of your signature. Outlook also creates folders stored in this location, with the images from your Outlook signatures inside. When you add images to your Outlook signature, Outlook actually compresses the images included in your email signature and saves them separately in a folder in this location. Outlook then attaches the images as you send them.