Can you describe in more detail your project? How many nodeMCUs do you have? How many sensors per device? What are you doing with the data that is collected on ThingSpeak?
Irrespective of the above, the recommended setup is one channel per device. This ensures that two devices do not end up in contention to update the same channel, given that there is a maximum rate at which each channel can be updated. You can then use MATLAB analyses or visualizations to read data from multiple channels and create a visualization that can be shared across multiple channels.
