I would suggest to you to do some research on motherboard quality and the VRM and heatsinks on various ones, in relation to the Ryzen 7. There are a lot of really good videos out by "buildozer" I think is his name on youtube and he discusses the quality of, and power delivery of those items with about every Ryzen motherboard out there.
Short version is that almost any B3/450 motherboard will have "enough" to do a Ryzen 3, and probably a 5. The issues particularly start creeping up when you move to the 7 and especially the X models due to the power they are going to require to stay stable.
Something else to mention. If you get a 1xxx of any Ryzen processor, pay close attention to the memory compatibility....there is a name for it that escapes me...within the motherboards website. They were very peculiar and particular about what RAM would work. This was alleviated significantly with the 2xxx series. IF you get a 2xxx make SURE to buy a 4 series chipset/mobo so that it will boot properly.