Primary vs. Extended Partitions

Yes, I believe that to be correct.

The structure of a Linux filesystem is more complex and more "intelligent" with respect to the way it organises itself. In your example, sda7 is probably "/home" - where all your user data will be written.

I've never run a Linux PC full time though, only occasionally and have a dual-boot set up on my laptop, so I'm not really knowledgeable enough on how it performs to draw comparisons between the two.