Multi-currency wallets are similar only at first glance. But some use the protocols of those coins that are able to store, and others have their own protocol allows you to operate different coins.
And what protocol does CoinsPaid service use for its multi-wallets?
What you mean? Protocol? This is blockchain technology.. Please read how works wallets

Thanks for support. Some people are crazy ^^
What currency pairs for conversion will you use at the initial stage of launch?
For now BTC and ETH, perhaps tey will be more.
Is it possible to set automatic settings for converting the received cryptocurrency to the specified currency?
Yes, but you need to write about this for technical specialists