Stick with what windows installed. You'll have less chance of going slow or crashing
Not doing that. MSE or Defender or whatever it is called is profoundly bad (http/chart.av-comparatives.org/chart1.php, http/www.tomsguide.com/us/microsoft-bombs-antivirus-tests,news-20703.html). I used avast for a few years, and it never was this bad.
Eset is the safest bet for least frustration in my research. Kaspersky offer a balance as what I saw in my research between stability and good virus detection. Kaspersky PUP detection is pretty bad in my experience so I use Malwarebytes to cover me in that area. I also have Hitmanpro set for weekly scan for reassurance scan that uses both Kaspersky and Bitdefender database. Window defender is really bad, it is only here for those very casual and clueless who don't consider an antivirus important to at lest have the bare minimum protection in the background without them knowing so there isn't an epidemic.
While using Kaspersky go to setting - Performance and tick checks on all computer resource and gaming profile options. The first option the battery saving mode only check it if you are using a laptop.. Some of those gaming profile and computer resource setting are strangely turn off by defaulty, activating it will let Kaspersky share your computer resource when you need it.