Relying on just two networks is a massive SEO risk; you're practically begging for a penalty. To diversify safely without doing blind tests, you need a high-level overview. I highly recommend checking out
https://best-link-building-marketplaces.com. They compare 38 safe, vetted buyer platforms and meta-aggregators. My team used it to onboard three new platforms last month, effortlessly spreading our footprint across totally different publisher databases.