Hello Addison,
Welcome to the Microsoft Community.
As for your information, I understand you have some issues with syncing files in OneDrive.
The options for choosing which folders can appear on your greyed-out device are likely related to the sync issues you're experiencing. If OneDrive can't sync certain folders properly, you may not be able to change the sync settings for those folders, causing the options to be grayed out.
You can try again on a different computer or network to see if the problem persists, as network problems are the most common cause of sync issues.
For more tips on how to troubleshoot OneDrive sync issues, check out this article:
Fix OneDrive sync issues - Microsoft Support
By the way, you can only mark or remove folders that are already in your OneDrive. Folders that aren't in your OneDrive (such as an external USB drive) can't be considered for syncing. Also, you can't deselect certain folders that are important to your PC, such as Documents, Desktop, Pictures, and your Personal Vault folder.
If you need any further help, feel free to ask me and I will give you more advice.
Best Regards.
William Yu | Microsoft Community Support Specialist