The "toaster" doesn't add power, so I doubt NS will be able to get close to the XBox One even.
You'll get a boost from full clock (rather than battery constraint), but that's not going to magically make the system like double or triple the power.
Memory bandwidth is going to be an issue here, LPDDR4 RAM isn't magically going to become GDDR5 RAM just because you have a toaster dock.
I'd expect graphics about double a PS3/Wii U honestly in real world games. For a portable device that's pretty good.
Game sizes should be in line with PS3/360/Wii U games, not much bigger than that. PS3/360 games are way smaller than their PS4/XB1 counterparts, NBA 2K on PS3 is like 8GB versus 40GB on the PS4, lol.







