Which global payroll platform offers the lowest fees and widest coverage?

The sad truth is - there is no one single platform that is standard and meets your criteria —worldwide. Sure, players like Payoneer, TransferWise, PayPal, Uphold, PaySafe, etc. will all tell you, that their system is the best and works everywhere, the truth is, there are many, many countries where such solutions either don’t work, or if they work, they are simply not the best / cheapest / fastest / most-preferred.

There are many companies that are specialists in mass payouts, it all depends on where the payments are originating and where they are going. How much is at stake, frequency of payments, FX, preferred last-mile method, etc.

Google for mass payout or payroll payout international, B2C payments, etc.

The names you have mentioned clearly do have an advantage on a worldwide scale, but they are not the de facto methods of payments, all things considered.