re: "Maybe Upwork administrators have any statistic."
No, they do not have any information they can provide about that. No statistics.
There is quite a bit of flexibility in what you can provide.
Posting here in the Forum and seeing if you receive any tips is a good idea.
Personally, as a client who has hired dozens of artists on Upwork, I do not look at attached files I receive when applicants apply to my jobs. So it doesn't matter what format the files are in or what they send.
I just look at artists' portfolios on their Upwork profile page.
But that is just me. I don't doubt that there are clients whose hiring practices differ from my own.
