Hi Davy. I'm Greg, 10 years awarded Windows MVP, specializing in Installation, Performance, Troubleshooting and Activation, here to help you.
I would use built-in Defender which gives adequate protection, best Windows performance, least issues, and is from Microsoft who knows how to protect their OS best. If you uninstall AVG, run it's uninstaller tool to get it all out here: http://www.avg.com/us-en/utilities. Then type Security in Search box, open Security Center and make sure Defender is turned on along with all other built-in protection.
If you want the best on-demand scanner install and run Malwarebytes free scanner. https://www.malwarebytes.com/mwb-download/. You can turn off the free trial in Account Settings to keep it only as a free scanner.
Here's a good guide to Bitlocker:
https://www.windowscentral.com/how-use-bitlocke...
Make sure it stores the key in your Microsoft Account as if you lose the key you will lose all of your files.
Due to this risk, I would have another backup method like built-in OneDrive Backup for your Desktop, Documents and Pictures with 5gb stored free explained here:
https://www.tenforums.com/tutorials/116029-turn...
or Google Desktop which will sync all your User folders to the cloud with 15gb free:
https://support.google.com/a/users/answer/99655...
Feel free to ask back any questions. Based on the results you post back I may have other suggestions if necessary.
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