Based on supply chain leaks, it's pretty safe to assume 12 GB memory with up to 100GB/sec memory bandwidth at best.
The A19 Pro had 12 GB and was around 77GB/sec memory bandwidth for reference. If I was a betting man, I'd say the memory bandwidth on the A20 Pro is the same.
If I didn't dream it, I think their presentation said something like 50% increase so you should be quite right probably around ~110GB/sec
Rumors suggested a wider memory bus on A20 Pro.
But they said the memory bandwidth was double the previous generation.