The only real metric by which financial terminals are judged is "Why don't we have any bloombergs? The bond traders are throwing a hissy fit."

Surely it gets noisy after 30 or so, but pedestrian stock trading apps like Thinkorswim have very high levels of customizability and modularity. I think even extensibility in Thinkorswim’s case. Java I think. Anyway, I would think any users of OP’s app are not using 90% of the 500+ widgets.

Panel is an arbitrary UX delimiter, so fundamentally no, unless you're really pedantic in defining (upfront) panel as a meaningfully semantic unit across apps.

Not really. The quality of data and latency are paramount, that's what you are actually paying for.