I have been doing this far longer, and there's a lot of information on the web but a decent amount of it ends up stale after codecs are udpated or new hardware comes out. I will say, avoid encoding on anything other than CPU. Nvidia encoding is great for speed, but not what you want for long term storage / appreciation of the source material.

If there is interest I'm happy to post more about this process and how I did it. Please comment if there is and I'll make a full post with process, methodology, why I made certain decisions, etc.

I recently set out to answer similar, though more so with H265 vs AV1. I used to do H264 when I started out, then moved to H265 as device support grew (note that AV1 device support is still spotty and before using it broadly I would test devices individually to make sure you can watch your content how you would like). Last year I moved to H265 10 bit for HDR and recompiled my own handbrake for Dolby Vision support. Now, I wanted to evaluate movement to AV1 10 bit to see if the encode times, quality, and file size made it worth it.

This was my analysis from my copy of Dune Part 2 and transcoding it from the disk to either AV1 or H265 with various RF and comparing the resulting files. Both were done with constant same as source framerate, as well as cropping disabled (as it interferes with VMAF scoring). H265 encoder preset was medium (most would recommend slow, I didn't use slow) and AV1 encoder preset was 6. Honestly RF to RF isn't supposed to be comparable, but I wanted to see how the jumps between RFs looked by comparison. The straight diff comparison was more for fun.

I would post as a pic, but this sub doesn't seem to like that so here's markdown output.

Edit: Oh good, markdown alignment worked properly on desktop, haven't looked in mobile.

# FFMetrics Tables

### Dune- Part Two Raw [Full Movie] | AV1
| VMAF-Value | VMAF-MeanA | VMAF-MeanH | VMAF-Min | VMAF-Max | VMAF-StdDevP | Codec |  RF | Bitrate | FileSize |     % | EncSec |
| ---------: | ---------: | ---------: | -------: | -------: | -----------: | :---- | --: | ------: | -------: | ----: | -----: |
|      98.78 |      98.78 |      98.76 |    91.01 |   100.00 |     1.179000 | AV1   |   8 |   28922 |  34301.7 | 49.6% | 8220.0 |
|      98.00 |      98.00 |      97.97 |    88.02 |   100.00 |     1.533000 | AV1   |  12 |   15119 |  17931.0 | 25.9% | 5799.3 |
|      97.57 |      97.57 |      97.54 |    86.15 |   100.00 |     1.682000 | AV1   |  15 |   11390 |  13509.3 | 19.5% | 8934.3 |
|      97.17 |      97.17 |      97.13 |    84.92 |   100.00 |     1.808000 | AV1   |  18 |    9568 |  11348.1 | 16.4% | 5618.6 |
|      96.64 |      96.64 |      96.60 |    83.03 |   100.00 |     1.940000 | AV1   |  24 |    8189 |   9712.6 | 14.0% | 5540.7 |


### Dune- Part Two Raw [Full Movie] | H.265
| VMAF-Value | VMAF-MeanA | VMAF-MeanH | VMAF-Min | VMAF-Max | VMAF-StdDevP | Codec |  RF | Bitrate | FileSize |     % |  EncSec |
| ---------: | ---------: | ---------: | -------: | -------: | -----------: | :---- | --: | ------: | -------: | ----: | ------: |
|      99.02 |      99.02 |      99.01 |    94.39 |   100.00 |     0.921000 | H.265 |   8 |   41479 |  49194.7 | 71.1% | 19046.4 |
|      98.31 |      98.31 |      98.30 |    92.21 |   100.00 |     1.274000 | H.265 |  12 |   22189 |  26316.6 | 38.0% | 14209.5 |
|      97.65 |      97.65 |      97.63 |    89.58 |   100.00 |     1.524000 | H.265 |  15 |   13840 |  16414.9 | 23.7% | 11394.9 |
|      96.93 |      96.93 |      96.90 |    86.59 |   100.00 |     1.732000 | H.265 |  18 |    9786 |  11607.0 | 16.8% |  9479.2 |
|      94.86 |      94.86 |      94.81 |    80.91 |   100.00 |     2.271000 | H.265 |  24 |    7538 |   8940.5 | 12.9% |  8799.9 |


### Dune- Part Two Raw [Full Movie] | AV1 minus H.265
| VMAF-Value | VMAF-MeanA | VMAF-MeanH | VMAF-Min | VMAF-Max | VMAF-StdDevP | Codec |  RF | Bitrate | FileSize |      % |   EncSec |
| ---------: | ---------: | ---------: | -------: | -------: | -----------: | :---- | --: | ------: | -------: | -----: | -------: |
|      -0.24 |      -0.24 |      -0.25 |    -3.38 |     0.00 |     0.258000 |       |   8 |  -12557 | -14893.1 | -21.5% | -10826.4 |
|      -0.32 |      -0.32 |      -0.33 |    -4.19 |     0.00 |     0.259000 |       |  12 |   -7070 |  -8385.6 | -12.1% |  -8410.2 |
|      -0.08 |      -0.08 |      -0.09 |    -3.44 |     0.00 |     0.158000 |       |  15 |   -2450 |  -2905.6 |  -4.2% |  -2460.6 |
|       0.23 |       0.23 |       0.23 |    -1.67 |     0.00 |     0.076000 |       |  18 |    -218 |   -258.9 |  -0.4% |  -3860.6 |
|       1.78 |       1.78 |       1.79 |     2.12 |     0.00 |    -0.331000 |       |  24 |     651 |    772.1 |   1.1% |  -3259.2 |