A. No, both features are measured differently.
The time parameter of "months", is based on the logic of a "week" being classified as 7 days. So in this case, 1 "month" would be 4 weeks or 28 days.
When using the "days" parameter, you can set the exact amount of days you want the cohort builder to look back.
Note: Both options are great tools to use when defining your audience.