There seems to be a cultural convention in Japanese that allows for "old" (simplified) versions of numbers to be used. An example of this would be the idol group 3776 which is known as "minanaro" and not "san-nana-nana-roku" as might be expected. This is similar to the old timekeeping system whereby simplified versions of zodiac animal names were used e.g. ね instead of ねずみ for rat, etc.
Is there a standardised list of simplified numbers, and when and how were they used? Is there a reason why the numbers are a mixture of simplified kunyomi and onyomi readings? Also, does the use of these numbers convey a certain sentiment e.g. does it sound deliberately archaic to use these numbers, or more sophisticated?
Thank you in advance for any input!