Player rating for tournaments across all installments of Heroes.

Option #1.
Everything is clear here.
Option #2.
Just one comment. With 2 participants, according to the formula, both will receive 100 points.

You are mistaken :) Calculate more carefully... 100-80=20.

Added 3 minutes later

I just think that the fractional part should be left, and not rounded down.

Rounding is done according to the rules of mathematics... But it's not essential. I did the calculation in Excel - it takes into account all the digits after the decimal point - and the result can be presented in any form with any number of significant digits. Although, to be honest, for the rating, one digit after the decimal point is quite enough...