Classic Shell isn't a necessity like with was with 8, but it still makes it more functional and less space-wasting. I was laughing "No" all the way to the download page as soon as I saw the tiled start menu.
Or you could just, you know, right click the starting tiles and unpin them from the start menu and then click+drag the right side to make it the width that you want.
Honestly I find my the current start menu after I put a tiny bit of work into it slightly more useful than classic shell is right now; the left side is still essentially identical to the classic shell, while the right side actually let me remove the bits of the classic shell menu that I don't often use and replace them with larger bits that I do use.
It still doesn't go quite as skinny as the classic shell implementation would, but it's close enough for me to not really make a difference and the easy button clicking and customization of the right side stuff makes it just as good in my opinion.
And yeah, the current version of Windows Defender is right up with the top AV programs in terms of protection efficiency. If you really needed another than Avast works just fine, just throw it a tosser email once a year to stop it from bugging you for a subscription and turn on gaming mode to stop the annoying popups and it works just fine. (As always note that while having two antiviruses might be useful in the event you need to scan your computer, you should never have more than one real time protection running at a time. Having multiple real-time protections turned on at the same time, in addition to slowing down your computer even more, can cause clashes between the two and actually cause them to
miss real problems due to the conflicts that they otherwise would have caught.)