Figuring out the quilting design is a big hurdle for me. I understand your concerns, a lot of time my review of my finished pieces is "another perfectly fine top ruined by inadequate quilting", my friends tell me a bit harsh but I'm really the only one that counts!
I'd probably be working with the vertical lines of the trunks in the panel, whether following them or echoing them. Do you have any fancy stitch options, like a serpentine or something vine-y? Just to hold that panel down and then do something related but a bit more complex/stabilizing in the rest of the top.
And the top is lovely! It is going to be good no matter what you do, it is made with love and will be received with love.
As another option, with my vision issues I have problems seeing/following markings so I will buy pantographs which I then copy onto parchment paper and sew through everything. It's still Free Motion quilting, but it gives me better results than either marking the top or by free handing. So if you wanted to try that, something like this would be a good all over option and pretty easy design.
https://www.urbanelementz.com/bird-on-the-wind.html