Let me add some detail to your coverage of the interconnects in relation to the more granular power markets. For example, ERCOT (Texas) has a 1:1 relationship

Let me add some detail to your coverage of the interconnects in relation to the more granular power markets. For example, ERCOT (Texas) has a 1:1 relationship with its market, but the rest are different. The Eastern Interconnect has many power markets made up of many many utilities. PJM, NYISO, ISO-NE, SPP, & MISO are the energy markets (called ISOs or RTOs) in the Eastern Interconnect. There is also the government owned TVA and Southern Company which is kinda like a large vertically integrated utility. These markets perform some of the most complex MIP models on the planet in their optimization. FERC Order #841 addresses the incorporation of storage into these markets.