Yes, the default buffer size may differ across languages.
I guess implementations with larger default buffer size performed better. Providing different buffer sizes in C++ and Python did not improve the performance drastically.
Yes, 6 times for each language and device pair.
I do not expect the measurements to change if the order is changed as they do not access the same file — a new file is created on each run.
I doubt the measurements will change drastically with the number of runs.
Thanks for the questions :)