Best practice to build a pergola type structure

Having patio pavers laid,
I want to build a pergola like structure for my home in the Northeast.

Something like this:

Questions about best practice:

1. Should I use tubular forms outside the patio?

2. Can I lay/secure directly on the (expensive) pavers?

3. 4×4 treated lumber ok?

Here is how I saw a display model done: