Softwares for GPU accelerated rendering I'm a YouTuber and I spend quite a lot of time solely to render my video (editing is sparse, mainly cutting boring scenes to keep the highlights of the episode) that I believe could be accelerated using GPU to render.

I've seen that most softwares use CPU to encode the video, however I was wondering if some of these softwares (such as Premiere which I haven't used yet) could accelerate the render process using both CPU and GPU.

I am currently using Sony Vegas, and during render while using CUDA, GPU load is around 20% which is a pitty I believe.
Adobe's CC suite will use the GPU, but the benefit you see from it depends on the power of your GPU compared to your CPU. This feature set is called the "Mercury Playback Engine" and contains, among other optimizations, CUDA support for certain realtime effects (scaling, crop, etc) as well as encoding/decoding. 

However, most integrated or mobile GPU's aren't powerful enough to make it worth using CUDA acceleration. Fortunately Adobe is smart enough to transition back to CPU rendering when it detects wimpiness in the GPU department.

With a dedicated graphics card like a GTX970 you'll see a significant decrease in render time - perhaps as much as 50% (so I've heard, anecdotally, from other youtubers like yourself).