EMB-145 flight crew reported electrical issues and safety concerns after landing and taxiing to the gate.

Narrative

Aircraft had MEL and APU generator button remained out as per crew procedure. Flight was uneventful until landing. After touchdown Engine 2 reverser amber and Engine 2 [reverser] disagree message. I announced spoilers; one reverser. Continued without incident and exited runway. After landing checklist was performed and after one minute idle/taxi thrust called for standard taxi. As number one was spooling down the electrical system acted as though dc bus two failed indicated by Multi-function Flight Display 1 and Primary Flight Display 2 screens blank. Except we still had Multi-function Flight Display 2 and RMU 2 and associated nav/com; transponder indicating IC 600 2 had power; and we still had nose wheel steering. The stick shaker was continuously active and we had a cascading set of master warning and caution messages and stopped the aircraft.The cabin pressure began rising rapidly and my focus then shifted to passenger safety. We ran the Quick Reference Handbook for pressurization automatic control failure (EAP 1-13) and regained control of the cabin pressure. The Flight Attendant called and said the emergency lights were on and I told her that we had an electrical issue; no emergency; keep everyone seated and we'd continue taxi momentarily. We ensured Engine 2 associated gens were showing online but I elected to restart number one for the additional 2 gens. We continued to the gate on both engines. When we set brake at the gate I gave the signal for GPU. The GPU was connected and verified 28 volts but I could not select the GPU with the button.The ground crew then opened the baggage door so I immediately shut down both engines. Keep in mind the beacon was on indicating that engines were running so I was alarmed to see the bag door opened. We deplaned passengers in an unpowered aircraft. I contacted maintenance to write up both the reverser and electrical issue. We were unable to select the GPU and neither batteries were controllable via battery selector knobs.Maintenance had me perform an electrical reset and seemed to fix the issue. I had a conversation with the Ground Personnel and asked them why they opened the bag door with engines running. They didn't notice that the beacon was on (it may have not been working as we had a plethora of electrical faults so I'll give them the benefit of doubt on not seeing a beacon); but...apparently didn't notice the running engines. Maintenance arrived at the gate to test the reversers and cabin pressurization and we swapped to a different jet to continue the trip.