If you want cheap and reliable PSU, you have to buy 2 PSUs: the cheap one and the reliable one. That's it.
This is actually with all components. The cheaper it is, the less quality components are used, and the less reliable it is.
For example;
My PSU: Seasonic PRIME 650 80+ Titanium [SSR-650TD], is the best 650W PSU money can buy and due to that, it also has 12 years of warranty. I've had my PSU in use since 2016 and it still is going strong, while providing me the tightest ripple, mythical levels of voltage regulation and highest efficiency there is. And all that while being dead silent. - This is the pinnacle of PSU build quality.
Review:
https://www.tomshardware.com/reviews/seasonic-prime-titanium-650w-psu,4690.html
I don't say that you have to buy the best. Good quality is also sufficient, like the 8 units i linked above. But what you want to buy, is either low or crap quality PSU.
That being said, fine, buy a cheap PSU. Learn the hard way why not ever to cheap out on PSU. Since when PSU fails, makes "pop", releases magic smoke, it has the ability to fry everything it is connected to. Aka your whole PC. Once that happens, perhaps then you look towards good quality PSU and a whole new PC as well, since all the components are fried by cheap PSU.
Since PSU powers everything, it is
the most important component inside the PC.
Btw, PSU reliability can be seen from the warranty length it has been given.
In a nutshell:
up to 2 years - terrible reliability
3 years - poor reliability (e.g Corsair VS/CS)
5 years - mediocre reliability (e.g Be Quiet! Straight Power 11, Seasonic G12, Corsair CX/CXF)
7 years - good reliability (e.g Seasonic Core/Focus GM, Corsair TX/AX)
10 years - great reliability (e.g Seasonic Focus GX/PX, Corsair RMx/HX/HXi/AXi)
12 years - superb reliability (e.g Seasonic PRIME)
Building mini-ITX build is often more expensive than standard ATX build. While the components themselves are smaller in size, they are also more expensive than standard ATX sized components, for the sole reason that not many people buy the smaller components. That, and it is also more expensive to manufacture smaller MoBo/PSU, since manufacturer has to somehow fit all the needed components inside far smaller area.
H370 chipset means that you will loose the OC ability of your CPU. If you want to keep the OC ability of your CPU, you have to get Z-series MoBo. E.g Z370 or Z390 chipset. Other than that, H370 chipset is quite good.