DX12 and forward, 3- and 4-way SLI is not supported. Which is to say, it might work if you try, but if there are issues, they're never going to be fixed. And as time goes on, game engines themselves will also drop support for the third and fourth GPUs and they'll go unused anyway. In short, now, there's no reason to consider 3- or 4-way SLI of any kind.