Which ground plane shape is more appropriate in my application?
Instead of Ground plane you should think of rerouting the PCB as there are many mistakes.

Lots of traces are going under components which may heat during work and cause issue.
High Voltage traces are too close.
Thickness of the traces are not according to current requirement.
Proper star connections are not there.

so please after doing all these things

Use a single ground plane with at least 30 mil distance from via or THT Pads.