1. I personally prefer Firefox. I think it's the only non-commercial browser, the safest one and the one with the best privacy policies. Not sure about that though.
Also beware: Windows explorer is different from Windows INTERNET explorer. Windows explorer is your file manager basically.
2. I don't like mcafee myself. I'm using ESET (paid version) which is very light on my PC, doesn't use much resources. I think there are some free virus scanners that are okay-ish but I prefer not to use them because I'm scared that looking for a free AV increases the chance of installing a virus that advertises as a free one.
Also, if you do find a free anti-virus, (almost) all of them only scan when you want to scan your PC, they don't do automatic scans or live-scanning.
3. Windows Explorer (not the browser, the file explorer), --> Go to "this PC" in the menu and you should see your drives including the total and free spac.e
4. Can't really answer to them. I don't think it matters that much but I can't say for sure.
5. That's really up to you. There's also "open office" which is simular to Microsoft Office, but I prefer the Microsoft one. You also can go for the subscription based one if you prefer, but I'm not sure which one is cheaper or better.
6. Onedrive bascially is your cloud for documents / folders/ pictures. I am using it (my brother pays for it haha) to backup my pictures from my phone. Also easier to redownload them on PC. But I also have PC files backed up to it. It's basically the same as Dropbox if you're familiar with that.
7. Since I recommend Firefox anyway
--> 3 bars top right --> Options --> Home --> Homepage and new windows.