That answer comes in the form of the Bracket system, which is WotCs attempt to hammer out some of the wishy-washiness of Commander and lay down guidelines for players to abide by
Its power and toughness will be equal to the number of Rats you control (not the number of Rats you controlled when the token entered the battlefield)
However, theres a very simple test that's almost foolproof to determine whether a card is a counterfeit or not, and today, I guide you through understanding the green dot test to help you identify genuine Magic cards and avoid fake ones
Destiny Spinner does come with some drawbacks, notably, it's a creature so it's more vulnerable to removal than say City of Solitude, and Spinner itself can be countered, which isn't a problem for more expensive options like Prowling Serpopard or Vexing Shusher
Equipped creature gets +1/+0 and can't be blocked