GPU encoding is fast, but usually it produces poorer quality results because it avoids trying paths that are hard to do quickly on the GPU.
If you want to optimise, try different encoders (sounds like you've already done some of this) and lots of different settings - it'll involve a lot of tuning if you want to figure out the right balance for your particular media between quality/speed/size, while also making sure that your machine hurts as much as possible.
Driveby 2c as a video industry person: don't retranscode your media unless you've got them in a really space inefficient codec and you're seriously hurting for space. You'll burn a lot of power retranscoding, are you actually saving useful $$$ of storage in exchange for that spend? Storage is cheap, and there's always a better codec coming along you could retranscode into and save some more space. It's a vicious cycle: each generation has to encode the artifacts from the previous generations.
Comments
GPU encoding is fast, but usually it produces poorer quality results because it avoids trying paths that are hard to do quickly on the GPU.
If you want to optimise, try different encoders (sounds like you've already done some of this) and lots of different settings - it'll involve a lot of tuning if you want to figure out the right balance for your particular media between quality/speed/size, while also making sure that your machine hurts as much as possible.
Driveby 2c as a video industry person: don't retranscode your media unless you've got them in a really space inefficient codec and you're seriously hurting for space. You'll burn a lot of power retranscoding, are you actually saving useful $$$ of storage in exchange for that spend? Storage is cheap, and there's always a better codec coming along you could retranscode into and save some more space. It's a vicious cycle: each generation has to encode the artifacts from the previous generations.