Contacting a researcher for academic queries, but he/she may be a potential reviewer?
Ignore the &quot;complications&quot;. It is overthinking the purpose of double blind review. If you want to ask them questions about their paper it is perfectly ok to do so.
After all, anyone in your field could be your reviewer in a double blind process. You don't need to be paralyzed just because you submit a paper.
If there are any ethical issues they are on the other side in deciding how and when to respond to you.