If you're referring to Toolbag 2, any normal map input is generally accepted.
There are options to have your mesh sync with normal maps baked in several different apps' tangent space, such as Maya, 3DS Max, xNormal, etc...
If you wish to use Object Space normal maps, there is an option for that in the material parameters Surface: property. You can also invert the red, green and blue channels of your normal map there.
If you want to plug in your normal maps that are correctly formatted for UE4 (i.e. MikkTSpace with the bitangent vectors flipped to match DirectX normal maps and the bitangent computed in the pixel shader), you have to change the tangent basis to xNormal/Mikk and then check "Flip Y" in the normal map parameters. The other situations are pretty straightforward.
Either will work, the only difference is the direction of the green channel, which can be inverted your 2D app or inverted (flipped) in the shader as shown above.
Replies
There are options to have your mesh sync with normal maps baked in several different apps' tangent space, such as Maya, 3DS Max, xNormal, etc...
If you wish to use Object Space normal maps, there is an option for that in the material parameters Surface: property. You can also invert the red, green and blue channels of your normal map there.
I hope this has answered your question!