I cannot answer that. What I can tell you is that when a micro-B USB cable delivers power to a USB device there are specifications for power limits, and some sort of fusing (including active fusing or polymer fuses which reset after cooling down) are part of that standard. When using the barrel connector the USB limitations are bypassed, and the barrel jack method of powering is superior to power over micro-B USB.
Some “fast chargers” may offer more delivery current, but it does not mean the device accepting the current is fused any differently. I cannot say for sure on the Nano, but just as a guess, I think the barrel connector method may have a couple of amperes delivery advantage.
The primary cause of boot failure, regardless of using micro-B USB or using the barrel connector, is the lack of ability to regulate with tight tolerances right at the moment of powering up. Even if a supply could deliver 5V at 25A, if the moment of power up is not well regulated, then boot will fail.
You might be able to use the pins for powering, I don’t know. The power consumption is rarely consistent, and this is modified by any attached peripherals. I have never heard of any trouble with the jumper for the barrel connector being an issue, nor have I ever heard of any of the power delivery methods having overcurrent issues due to pins being stressed. Due to the multi-layer fine pitch circuit board traces I will definitely recommend not soldering anything. I think pins are sufficient if needed, especially if it can be delivered across multiple pins, or better yet, delivered through the barrel connector.