Which neighborhood: Back Bay, Beacon Hill, North End or somewhere else?

I'm being transferred to an office in the Downtown/Financial District neighborhood later this fall and struggling to identify the right area for me to live.

I'm currently in Manhattan, so city living is my comfort zone, and I won't be bringing a car. Looking for a place with easy access to parks, supermarkets, restaurants + nightlight options. Strongly prefer to be within a few blocks of a T station -- with a sub 30 min commute -- so I can explore all that Boston has to offer. Safety is a priority as I'm 40F & single and don't want to rely on Ubers when working late. Still finalizing budget, but aiming for a 1 bd/1ba at or below $3,500. Clean and quiet are musts, but amenities are not. Thanks in advance.