Max number of Regions

New to Cockroachdb here, a general question on replication and deployment topology.
How many regions can Cockroachdb support? What is the performance penalty if there are big number of regions (hundreds to thousands) given Geo-Partitioned Leaseholders Topology or Duplicate Indexes Topology use cases?
A example here. If I have 3 regions, I want the read to be local/fast and write replicate to all 3 regions reliably. I guess I can use Geo-Partitioned Leaseholders Topology or Duplicate Indexes Topology. Now if I have 3000 regions, I think read won’t change much but how will the write latency looks like? Similar to 3 region, or 1000 times longer?

Thanks!