With regards to differences with 'normal' Python, depending on WASM also means that despite having the same sys.get_int_max_str_digits() = 4300, my local Python can print out (2222*5555 + 5555*2222) in its entirety, while the browser based one can't.

Values that can be set via maxdigits in sys.set_int_max_str_digits(maxdigits) are also limited to size of int in C.

It’s basically the same speed as Pyodide for cpu bound work. It is overall about twice as slow as native Python on the exact same machine. There is a benchmarks folder in the CoWasm git repo with a several dozen benchmarks.