Symbols for "YES" and "NO" in formal English writing
Solution 1:
X for No and O for Yes are clearly understood by everyone in Japan, but not in English. In fact, in my first Japanese class in the US, when the teacher used these symbols, I thought that X meant Yes because "X marks the spot."
In my own Japanese to English translation, for tables, I usually spell out "Yes" and "No." For the circle, triangle, and X (i.e., three-level symbols), you can use, for example, A, B, C or Excellent, Good, Poor, or any other easy shorthand.
If you do use the Japanese-style symbols, you should use a key at the table to explain the symbols because they are not readily understood by English speakers.
Using a checkmark in a table is fine for Yes. In that case, however, there is no need for an X for No because the absence of the checkmark implies No. You can also use a solid dot symbol for Yes (opposite of the Japanese meaning), and again the absence of the dot would imply No.
Solution 2:
I am a native English speaker, with what I hope is an above average education. I can think of no good reason, especially for a conference paper, to use anything other than "Yes" and "No" when what you mean is "Yes" or "No".
Solution 3:
I'd also consider using Y for Yes and N for No. I think this is clear for everyone speaking English. It may look worse in the manner of design but will be understood by all.