Now that is a loaded question! The answer ranges from none, to everything else.
One thing depends on whether you are dedicating your PC to DAW only, or using it as a multi-use PC. If it a dedicated studio DAW, maybe the best plan is to disconnect it from the network and use offline updates only. You only need an on-demand scanner if that is the case. No real-time AV protection required, which frees up a bit of RAM and some CPU cycles.
But if you are going to be connecting to the internet, you need some protection.
A lot of folks take their chances with Windows Defender, which has improved with Windows 10. It doesn't always score the highest detection rates in tests, but it is free and included with Windows. Since it is embedded in Windows some folks feel that it has the lowest system impact.
Many AV file scanners let you set some exclusions, so you can prevent your audio drives from being scanned, for example. Or you can disable real-time scanning while you are working with audio.
IMHO, if you want the best paid protection, Bitdefender. Kaspersky, and Avira are consistently among the best in 3rd party tests year after year.
The best free products are probably Avast, Bitdefender, and Avira. For free plug and play with the broadest coverage, if you don't plan to install more than one product, my vote would go to Avast Free. In addition to the file shield and web shield, it now has a behavior shield. Just be sure to select the custom install, and uncheck the extras you don't really need.
https://www.avast.com/en-us/free-antivirus-download Good luck! You are likely to get some interesting opinions on this subject!