Dear respected,
As per the description, the first concern is you don't want OneDrive to sync all of your personal files. If so, please refer to the article to stop it syncing all files and then only select specific files or folders to sync as you need.
See: How to cancel or stop sync in OneDrive - Microsoft Support

And the second and main concern is, it seems like some of the files are not syncing successfully as you can't see them on the other PC. If my understanding is correct, please first make sure the files have been synced correctly to your OneDrive space. To confirm this, please check if the file is in OneDrive Online via browser.
If it is not in OneDrive online, it means the sync issue is happening on the original PC. If it is in OneDrive Online, it means the sync issue is happening on the destination PC. And to fix this, please try to sync one single file at a time as testing and see if the same sync fail issue will happen. Let me know if there shows any error message which will help the troubleshooting more efficiently.
And for the sync issue OneDrive PC, please do Reset OneDrive - Microsoft Support
Appreciate your understanding that sometimes the initial reply may not resolve the situation very soon. However, we can work together to narrow down and resolve the situation. Please kindly post back and provide the more information, then we can focus on your specific scenario and provide specific suggestions.
We'll be here for you to wait for your updates. I appreciate your time and effort on checking these above and thank you for your patience and cooperation. I hope that you are keeping safe and well!
Sincerely,
Mia | Microsoft Community Moderator