I would say the easiest way is a chauffeured car such as Lyft. No worries about parking, no bother parking and fetching a car particularly if it is raining.
Best? There is a heat wave where I am as I type this and I will not be in an air conditioned Victorian styled high ceilinged library where cookies and tea would be served so I will wisely stay away from that highly controversial question.
Practically all of the time you can park at Boardwalk to have dinner there, visit the resort, attend a wedding or other event there, etc.
If, say, you are also going to Epcot you will need to arrive at BW to park about just in time for your BW activity and to drive out of the BW area perhaps to Epcot's or Hollywood Studio's lot when you are finished with activity at BW.
However you may use valet parking and arrive any time and leave your car there all day unless the valet tells you otherwise when you drive up to him/her. (Resort valet parking also allows hopping among other resort valet lots all day ).
There are some busy time and dates where you would not be able to park yourself at BW unless you have a specific reservation for something such as a meal there. Like theme parks when they stop admitting guests due to crowding, the parking lot guard may apply different rules during busy times. Frequently, free parking at a resort is expressed in terms of a 3 hour limit.
Gondolas are expected to begin operation at the end of September 2019. The general rule is that when you board you will get off at the next stop. From Pop Century you would get off at Caribbean Beach where you can transfer to your choice of the Epcot or Hollywood Studios gondolas. (The exception is Riviera resort where, if you arrive there you remain on board the gondola if your destination is further on. Riviera station is expected to open in December 2019, when that resort opens.)