It's more than one mile to walk from HS to Epcot International Gateway, it's a pleasant walk but definitely not short, and once you get to Epcot Norway is still on the other side of the lake. The boat is not fast either because it stops at all the resorts along the way. It can't be more than 5 minutes to drive between HS and Epcot parking lots, but you have to factor in walking or taking shuttle between car and the park entrance. Pretty sure you can also take the bus between HS and Epcot. I would wing it based on weather, how I felt that day, etc.
This sums it up the best. My husband and I frequently will star the day at the Studios and we almost always end our days (any day) at Epcot so we are well versed with the boat versus walking versus bus thing and also with driving from park to park. I would say not to drive between the parks, just leave your car at the Studios since that's where you want to end up at night. We usually will park at Epcot since that's our ending point and then go through Epcot and look at the weather and our feelings and if a boat is sitting there at the International Gateway and then decide how to get to the Studios. You just do the opposite for how to get to Epcot.
Once out of the Studios, the boat ramp will be to your left. Check to see (1) if a boat is approaching and (2) how long the line is. If the line is well beyond the awning of the ramp, you might want to think about walking. Just past the awning is fine and maybe even a bit more than that since once the boat gets there, the "compressing of the line" factor hits and people will start to move forward.
If the weather is good and you want to walk, just follow the signs to the walkway (to the right of the boat ramp). Now, here's the good part. Once you get to the point where you go to the left (on the other side of the canal), there will be a bus stop there marked for Epcot. If a bus is sitting there, get on it and save yourself the walk. If not, just keep going and see some things you might not normally see.
And the best thing is that if none of these options appeal to you at all at the time, you just head to your car and drive.
So really, I wouldn't "plan" on anything now. Just wait until you are leaving the Studios and then decide.
After your meal, I would seriously take the boat back to the Studios as you will probably be full. Or, you can walk to one of the Epcot resort hotels and then take the boat to the Studios.
Your choices are a lot of options for what you feel at the time.