Caroline T.
Yelp
King Street station is indeed one of the more beautiful stations you may come across, however I'd caution any tourists to be extra mindful of their surroundings and belongings if they choose to walk around.
Masks are currently enforced inside the station and on the platform, but doesn't seem to be if you're waiting for Uber/Lyft or the buses.
If you Uber/Lyft to or from the station, you'll be dropped off at the entrance. If you're taking an Amtrak bus (even the 'thru bus'), you'll be picked up at the left of the entrance (guards inside can confirm this for you, when I was there at 8am there wasn't an Amtrak worker in sight).
I took the Amtrak thru bus to Everett, and we left King Street on time. However, we ended up stopping at a Greyhound station nearby to pick up additional passengers (waited there about 20-30mins, for some reason the passengers weren't allowed to board until the last 10mins).
If there was a cafe or a coffee stand in the station, it wasn't open when I returned on Saturday around 11am. If you are hungry and have some time, there is a restaurant a few feet away called "13 Coins" or there's a Starbucks across from 4th Ave.
Also, be mindful that the station is near Lumen field. If there are any games, concerts, or conventions the area may be harder to get to if you're in a rush.