[tebasuna51]

Using my son PC:

nvencC64 --check-features
NVEncC (x64) 4.47 (r1188) by rigaya, Sep 1 2019 06:07:40 (VC 1916/Win/avx2)
[NVENC API v9.0, CUDA 10.1]
reader: raw, avi, avs, vpy, avhw [H.264/AVC, H.265/HEVC, MPEG2, VP8, VP9, VC-1, MPEG1, MPEG4]

Environment Info
OS : Windows 10 x64 (18362)
CPU: Intel Core i5-6400 @ 2.70GHz [TB: 3.09GHz] (4C/4T)
RAM: Used 2459 MB, Total 8119 MB
GPU: #0: GeForce GTX 1060 6GB (1280 cores, 1784 MHz)[PCIe3x16][436.15]

List of available features.
Codec: H.264/AVC
Max Bframes 4
B Ref Mode yes
RC Modes 63
...
10bit depth no

Codec: H.265/HEVC
Max Bframes 0
B Ref Mode no
...
10bit depth yes

Encoding the same sample:

"NVEncC64.exe" --output-depth 8 --vbrhq 0 --vbr-quality 23 --preset quality --bframes 3 --ref 3 --bref-mode each --lookahead 32 --weightp --aq --direct spatial --sar 1:1 --colormatrix bt709 --chapter chapters_3D_delay.ogm.txt --key-on-chapter --fps 24000/1001 -i "__ENCODE_3D_MOVIE.avs" -o "00009_3D.264"
weighted prediction with B frames unsupported.
NVEncC (x64) 4.47 (r1188) by rigaya, Sep 1 2019 06:07:40 (VC 1916/Win/avx2)
OS Version Windows 10 x64 (18362)
CPU Intel Core i5-6400 @ 2.70GHz [TB: 3.29GHz] (4C/4T)
GPU #0: GeForce GTX 1060 6GB (1280 cores, 1784 MHz)[PCIe3x16][436.15]
NVENC / CUDA NVENC API 9.0, CUDA 10.1, schedule mode: auto
Input Buffers CUDA, 44 frames
Input Info Avisynth+ 2.60(yv12)->nv12 [AVX2], 1920x1080, 24000/1001 fps
Vpp Filters copyHtoD
Output Info H.264/AVC high @ Level auto
1920x1080p 1:1 23.976fps (24000/1001fps)
Encoder Preset quality
Rate Control VBRHQ
Bitrate 0 kbps (Max: 24000 kbps)
Target Quality 23.00
Initial QP I:20 P:23 B:25
VBV buf size auto
Lookahead on, 32 frames, Adaptive I, B Insert
GOP length 240 frames
B frames 3 frames [ref mode: each]
Ref frames 3 frames, LTR: off
AQ on(spatial, strength auto)
Others mv:auto cabac deblock adapt-transform:auto bdirect:spatial
encoded 158712 frames, 71.31 fps, 8429.56 kbps, 6651.93 MB
encode time 0:37:05, CPU: 60.5%, GPU: 5.9%, VE: 24.6%, GPUClock: 1674MHz, VEClock: 1505MHz
frame type IDR 671
frame type I 671, total size 110.00 MB
frame type P 42468, total size 3410.40 MB
frame type B 115573, total size 3131.54 MB

Encoding finished 09/09/2019 15:25:54,18 -> 37:08,76

Of course is fast but not to much with parameters like x264 defaults
(with x264 default weightp is mode 2 and lookahead 40).

But the bitrate obtained is near double, maybe the crf equivalence is not the same number.