Should I put my bitcoin wallet on an encrypted disk or not? Is it really beneficial to put my bitcoin wallet on an encrypted disk (LUKS encrypted)?
This only helps when someone malicious has physical access to you hard drive while your computer is not operational (shut down, account logged out, screen locked, etc.). When your operating system is running, an attacker running malware on your machine won't even notice your disk is encrypted.

Make sure your wallet is encrypted. That's much more important. Of course, having your disk encrypted has other benefits but as long as someone with physical access to your machine isn't trying to steal specifically your money, there is no advantage in this regard which would not already be there if you used an encrypted wallet. But the latter has the additional advantage that malware capable of reading your files can't just send your private keys to the attacker when you're using your computer and your files are available.