HAhaha, I swear you are in my head!!! I just demolished the two old planters I had because i had fashioned them out of untreated wood and after five years they were beginning to look a bit sorry for themselves. I was looking at my leftover timber and was thinking, Couple of planters, no bother!
I am seriously tempted with a pergola now!
The one thing to pay attention to is weight. You want the "roof" to be as light as possible. But you also want the weight from the posts to go directly to the ground. If you don't want to bury them, make sure that they are directly above the posts that your deck uses (which are buried).
Here are some other design ideas
https://www.thespruce.com/free-pergola-plans-1357132
And finally, because this guys voice is awesome. (but he has some good ideas).
Hehe, as soon as I get my little ones to bed I will be watching that video.
I have some posts sticking up at the end I could have it onto. My original thinking was some kind of trellis affair to screen out my neighbours. Opportunities abound!!! Might have to wait for next year though. I don't think I could handle another project so soon!!