Answers
There is no legal framework to get a Greek citizenship at this moment.
There is a restriction on those with dual citizenship status as per the Greek Golden Visa program. You can decide with which passport you want to proceed in your application. Issues under consideration are the following: enter Greece legally with your American passport, you don't need a Schengen visa in contrast with your Russian one. Also, the bank requires certified documents concerning your permanent residence and your profession/income status for the opening of your bank account. Also, take into account the COVID-19 regulations for your entrance to the country. All such issues are being smoothly facilitated if you decide to proceed through the remote implementation option, which was voted by the Greek government at the end of the previous year. There is one important clarification to the given information. All this is applicable for the Greek Golden Visa program, residence by investment program, not the citizenship one. Greece does not provide a CBI program at the current moment.