When powering a Nano via Vin, it's recommended to use 7-12v.
When powering the Nano ESP32 via Vin, it's recommended to use 6-21v.
If I were building a project with some 5v led strips, this presents a dilemma. The LEDs need a 5v supply, with a ton of wattage, so that's one power supply that's definitely needed - but how to provide power to the board, just a couple of volts higher (if going to Vin)?
To solve this, could one solution be to get a USB power cable and take a feed off a 5v power brick? With the bulk of the power going to the LEDs.
e.g.
This is of course meant as a final power solution, when you're not uploading anymore, and once you're ready to package the project up, and leave it on a Nano board, etc.
Firstly, you say you have 5V available. The classic Nano can be powered by connecting 5V to the 5V pin (I think of it as an input, or an output only for very limited current purposes), so that is your best approach.
For the ESP, yes, I would expect it could be powered via a USB connection using a 5V brick. The online documentation is fairly clear about that. However, a separate source should be used for the LEDs, unless the 'brick' has enough current to drive the whole setup(with a proper 80% derate; so, if it's a 5A brick, plan on loading it to 4A max; this is applicable to just about any DC supply). I'd also try the brick with a suitable load, to ensure it behaves under steady-state high-load conditions, though, before trusting it. I've thrown away more than one.
The datasheet for the Nano shows the 3.3v and 5v pins as "out" (from what I can tell), is that only if vin is providing enough to be down regulated for those pins?
The Arduino Nano can be powered via the Mini-B USB connection, 6-20V unregulated external power supply (pin 30), or 5V regulated external power supply (pin 27). The power source is automatically selected to the highest voltage source.
However, I rarely trust pages that are chiefly devoted to the 'sales campaign' for authoritative information, so see also the discussion here, for nuances:
Upshot, they "don't recommend it", but don't quite suggest it's verboten. Still, for the clone Nanos I use, I have not encountered a problem with doing so; I guess it may bite me, but so far, not.
One could also go to the datasheet for the particular regulator used on your Nano, to see whether there are any hints about what happens if voltage is applied to it's output without any input voltage. Might be worth a read.
YMMV. A $1 boost converter to produce 8V from 5V(be sure to power it up and adjust it's output without the Nano connected) for powering the Nano would seem to be simple, but I grant you it's more hardware.