InForm runs your script on Rhino Compute in the cloud. Each time, the server 'reopens' the grasshopper script. This is slower than using it local.
Mesh size, Grasshopper file size, and distance to the server (in Europe) has a large impact on the performance in InForm. This can add 1-2 seconds to each iteration.
Iterative workflows like Kangaroo or Galapagos are not supported.
Max runtime is 5 minutes. Longer runtimes are possible, but only using the 'batch' feature.
Max size of the Grasshopper script is 50mb, although it is heavily recommended to use the File Input component instead of internalizing geometry.