In this context, the B word is meaningless.
Even worse, misleading.
Lets consider your current parts.
GTX 1070 SC with a i7-4790k.
Let's assume that some 'bottleneck calculator' shows you 10% bottleneck. (whatever that means)
Lets further assume that in some game you play, you get 100FPS on medium settings.
That is our baseline.
Now, lets swap in a really good GPU...a 3070.
Change nothing else.
The "calculator" will go bonkers, and tell you there will be a bottleneck of 45%.
Sounds really bad, right?
Wrong.
Given only changing the GPU,
you will still get the same 100FPS, but you will be able to turn the graphics level up to High.
The CPU provides the frame rate, the GPU applies the eyecandy to those frames.
If you were to go really silly and swap in a 4080ti GPU,
you would still get that same FPS, but you'd be able to turn the graphics level up to "CountThe NoseHairs"
But the calculator would probably break in trying to go past "100%"...
When changing parts like this, it is often possible,
even likely, to get both better performance and have a
worse "bottleneck percentage".