I think you will find that the RPI current requirements considerably exceed the originally specified current limits for micro-USB connectors. It has never been a problem. You shouldn't have any issue with soldering directly to a micro-USB connector for your power. Connecting to the 5V GPIO pins has a little more risk, as there is no protection on those pins.
BTW, I use one of these for 5V supply. It works great, but I am finding that if it is disconnected from a load, it generates RF noise in my radio.
https://www.amazon.com/gp/product/B00FXNN7YA
I would stay away from the 3A buck converters. A few of us have tried them and found they didn't perform well.
BTW, I use one of these for 5V supply. It works great, but I am finding that if it is disconnected from a load, it generates RF noise in my radio.
https://www.amazon.com/gp/product/B00FXNN7YA
I would stay away from the 3A buck converters. A few of us have tried them and found they didn't perform well.