Hi, I've only ever boarded in Barbados. Yes you have to get off the ship and go through customs, but the walk is no where near 4 miles. Also the process is fast and painless. The meeting time to get off the ship has always been 8 am in my experience. And you meet in the lounge, also you have to fill out a customs form. I am not sure if you have to stay off the ship until a certain time because we always come back in the evening after a day of shopping.
You don't need to pack or take off you luggage. You can dress for you day touring and just get off and do your thing and get back on after.
Yes evening meals are stopped early in the evening for the drill and there are serious about the closed time. Even being a minute after the time, you are not aloud to join the line and there is a worker there taking up the pans after the last guest in line is served.
Any other questions? I will be happy to try and answer.
Ps. This only relate to guest who start their cruise in Barbados