Extending an RF ground plane outside a small PCB
Once happened something similar to us, also at 900MHz. We had a ceramic antenna soldered in our PCB with a very small ground plane. As the performance was very poor we contacted the antenna manufacturer and they propose adding a copper tape directly to our ground plane, that improved a lot the efficiency.

The copper tape was something like this: https://www.sparkfun.com/products/10561

So yes, increasing the copper plane length improves the efficiency of the antenna. From this presentation from Laird you can see: https://connectivity-staging.s3.us-east-2.amazonaws.com/s3fs-public/2019-04/engineers-approach-antenna-selection-implementation-webinar.pdf


About option one or two. The option two sure works as it is the same that we did. But I am not sure that the option one doesn't work.
Hope it helps!