I'm trying to completely understand the purpose of Node-RED and how one would use it and what they would use it for, so I can know if it's right for me... Is it like Stringify or IFTTT? How would someone who has Insteon and Phillips Hue benefit from this?
From my point of view
I came to Node-RED from the block programming language Scratch which lets you "write" programs without having to type a load of text.
Node-RED has that in common with it - you just choose blocks (nodes in this case) from the menu on the left and join them together using wires to make some piece of logic that does a job.
Node-RED has the great advantage of being able to easily communicate with other systems - particularly using the easy to comprehend MQTT protocol and makes it trivial to use MQTT messages.
Please also do some searching through the forum since I've written about this before in response to similar questions. I need to go do some other stuff right now but if others haven't already steered you in the right direction, I'll try and add some more detail later.
You seem to be thinking along home automation lines so I'll say this. NR is great for home automation - where you want full control yourself. Things like HA and others might be simpler to start with but may not allow such easy full flexibility. You can use it to replace large amounts of IFTTT but the focus is different, more on local, less on cloud service integration (though there is plenty of that too). Benefits to Insteon/Hue users would be the ability to do things that the "official" apps can't and to, in some cases at least, be able to continue working if your Internet goes down.
I come from OpenHAB and was disappointed there with the complexity of rules and the configuration at all.
I currently use Node-RED in my own home automation on a Raspberry Pi 3b with Zigbee switches and bulbs, tasmota plugs, Enocean devices, IR sender and a Sense HAT. Node-RED can connect all those different protocols and devices in one dashboard / programming interface.
But I use Node-RED also at a customer to print out labels after reading the weight from the serial port of a scale: The Raspberry Pi has a button connected to GPIO 18, which I can read directly in Node-RED. After pressing the button, Node-RED reads the serial port (via an USB-serial adapter), extracts the weight and prints it to a Brother QL-720 label printer. The "solution" from the manufacterer of the scale was a Windows program, that pasted the weight in another Windows program, where I had to print the label manually. The cost of the program was double the price of the Pi with all accessories and programming.
Check out the share your projects forum category for examples of how other members are using node-RED, and the diversity of what can be achieved.
Compared to other solutions, Node-RED excels in managing heterogeneous hardware and software configurations, with a minimal requirement in resources.
A Raspberry Pi Zero Wireless provides enough power. Additional nodes allow to connect virtually anything, like SQL databases, remote AI engines, dedicated sensors, GPIOs and I²C bus, et al.
I'm using Node-RED primarily for IIoT or Industry 4.0 projects.