Well, I don't think any of these really matters if you are just using a PC for trading because all you need is a browser with an internet connection.
The security does play a role if you are storing your coins in your PC because you would want to protect your private keys with higher security.
Any PC would do fine. I use an intel i3 laptop with 4 gigs of RAM. I don't use a VPN, I just use a hotspot from my phone and without any antivirus for my own reasons.