I have an LED control project that uses an ESP32 dev board and a TFT and rotary encoder. Rather than making a PCB or protoboard for it, there are so few interconnets that I could actually do them all with dupont cables (or wahteve the standard female to female breadboard cables are called).
The only problem is power and ground, where I'd need a 3-1 splitter, but I don't see dupont cable splitters.
Is it crazy talk to assemble a project box wired that way? Seems a lot easier and less error prone than making a board.
but I don't see dupont cable splitters.
So make one. Cut two wires in half and strip the four ends and solder them all together. Then you have a three to one splitter.
Is it crazy talk to assemble a project box wired that way
I would say so. Things need to be soldered up to be reliable. Otherwise it is subject to vibrations.
Are you planning to connect the TFT and encoder via cables either way? If so, it might seem pointless to solder the ESP32 board to a protoboard just to break it out to header pins when the ESP32 board already had header pins on it.
However, I've noticed multiple individual dupont connectors are less secure than a single multi-wire dupont connector, and thus more likely to fall off or get a bad connection over time. Connecting wires directly to the ESP32 board, it's less likely that all the necessary pins will happen to be adjacent to each other, whereas you can design your protoboard for the specific connections your project needs.
I've noticed multiple individual dupont connectors are less secure than a single multi-wire dupont connector,
True but even that is ropy, what is secure is two rows of a single multi-wire dupont connector either side of a PCB. That is the most stable configuration.