I'll chime back in.
4g is plenty and if you are using Firefox it is not using anywhere near 3G all the time.
Here I have a laptop with 4G ram running Firefox.
The Wife's computer has 8G ram using mainly Chrome.
My new desktop has 16G ram using Firefox.
All can use WiFi.
When on WiFi at home, you will not see any difference between any of them accessing the same web pages.
Internet speed and spies have more to do with reading the news that ram.
Adfender works well.
I am also trying Ghostery (free).
Ghostery will show you what is spying on you. Then you have the option of blocking them. The program remembers it and the next time any site comes up it blocks it again for you.