"Only domains with minimum metrics (like TF 15+ DA10+ etc.) will give me results."

Wrong! metrics has nothing to do with SEO-value.
As we explain in this article, metrics has not much to do with SEO-value - the reason you buy SEO-domains.
To get SEO-value you need to focus on the backlinks themselves and make sure there are plenty authorized and quality ones (we talk about how we analyse backlinks in this article). All our domains are being analysed by experts according to their individual backlinks, and we ensure that all our domains are loaded with authorized-high PR-natural-diverse backlinks for certain SEO-value.

"I must buy a domain with the exact niche as my money-site in order to get SEO-value."

Wrong! you will get SEO-value from any domain with authorized backlinks.
It's important to understand that the SEO-value (or "juice") is being passed from the backlinks. Authorized backlinks with high SEO-value will pass that value regardless of their niche. Obviously, having a niche related backlinks for the domain you get is a plus, but it's definitely not a must. Especially if you're using the domains you get as PBNs, in that case the backlinks of the domains you buy are 2-tier backlinks which nourish your PBN with general SEO-value, then you can focus that SEO-value to the specific niches you need by controlling your PBN.
It's always important to distinguish between money-sites niches to real-life/natural sites niches. We only deal with 100% spam-free domains which are natural, meaning they used to be real-life websites (usually informative/academic or websites of businesses/companies), only such kind of domains have natural backlinks from authorized sources and that's the only way to go in order to get any SEO-value.
Money-sites, usually, have niches that are not popular among real-life websites and therefore you simply can't find real SEO-domains in those niches. The way to go is to get SEO-domains that have backlinks that are somehow related to the niche you want to promote. For instance - for a weight-loss related money-site you should consider any domain with backlinks related to health/food/exercise/sports etc. It is important to know that even if you buy a SEO-domain that is not related to your niche at all, you would still get SEO-value out of its authorized backlinks regardless of their niches.

"The name of the domain is important for SEO."

True & Wrong. If you're using the domain as part of a PBN then the name is not very important as its only reason is to mediate between the authorized backlinks to the money-site (or even to another PBN). If you're using the domain as a money-site then the name is somewhat important since you want to be as natural as possible and using an unrelated name or a name that makes no sense might looks suspicious.