Old wiring to new wiring
The kinda' red wire may have been there so a switch can control one half of the outlet (receptacle) unit.
It is r4ecommended to run a new cable for the new receptacles, etc. all the way back to the panel. While the metal sheath around the existing cables can be a grounding conductor, it may or may not be sufficient and some additional examination and tests would be needed to determinine if it is.
The disadvantages of crab apple trees. In summer, the apples are too sour to pick and eat. In winter the birds come and leave dropping all over the place.