I find a picture is worth a thousand words (in this case),
@jenhelgren .

For the sake of this discussion, let's focus on the Outpost Bus Depot (bottom right) and Settlement Bus Depot (upper left) initially. There are 3 internal bus lines (Orange, Yellow, Purple) that run back and forth between the two bus depots. So, for example, when
@Stratman50th says the Yellow runs to WL, what actually happens is a Yellow Bus leaves the Outpost BD and runs down the east side of the Fort (follow the yellow line on the map) and gets to the Settlement BD. Then it CHANGES its signboard outside over the driver's head and will say "Wilderness Lodge". THEN it will take you to WL (and back to Settlement, flips to "Yellow", and runs back to Outpost BD).
I will add it is USUALLY the Yellow that runs down to WL and back. Just watch the overhead sign boards at the Settlement BD or ask the driver.
In the mornings you can take a bus to MK from the Settlement BD (use internal to get there). A dedicated bus runs back and forth in the morning between FW and MK - also dedicated in the evenings. Midday it often stops each way at WL as well.
To get to MK you can also take the boat from the dock at the Marina (top). It will arrive to run to MK 1hour 40minutes before the official opening time. So for 9am official, it gets to the Fort at 720am or so (holds a lot of people) and gets to the MK dock about 745am. The MK gates open at or slightly before 8am, you walk down to the hub and to the right toward the teacups and queue up for the Early Opening at 830am (CM's scan MB's at the hub to allow Early access).
That's how internals work and transport to MK. Buses run to EP, AK, HS from the Outpost (catch an internal in that direction) as well as Disney Springs. Those locations also send buses back to the Outpost on the return trip.
Honestly we boat to MK and drive to the other parks (no difference bus or boat really to MK). Boat puts you close to the front gate. The other parks make you wait for an internal, then wait for a park bus, and then the bus depot at the parks is a walk too. So we just drive from our campsite/cabin to the EP, AK, HS lots and walk it in there.
Since you're going to be in a cabin, you can take an Orange or Purple bus in which ever direction you want to go. Just be aware there is NO automobile parking down by the Settlement BD, Marina, or Pioneer Hall (Trails End, HDDR) area. And there is VERY limited parking (6 spots) at the Meadow Trading Post which is near the campfire singalong movie spot (no parking either).
My map was from our January 2024 stay. Good luck!
Bama Ed
PS - the boat between FW, WL, CR only runs in the afternoons/evenings and then only in one direction (don't know which CW or CCW). So we just take the bus to WL from Settlement which is not bad at all.