Hey Promo,
This was a while ago I tried this so I downloaded the newest handbrake and am running some tests. This time the source is a BD rip on a NAS with native BD file structure. It's being saved on the local computer on a mechanical drive - SSD only had ~30GB free and I didn't want to risk it. First run using H264 1920x1080, frame rate is same as source which I'm assuming is 24fps and I used constant frame rate. The original was 33GB but that is the entire BD, menu structure, extras and all, so I would guess the feature was about 25GB I'm guessing. With the video quality slider set at the default 22 the conversion took about 50 minuted and file size is 2.5GB. Sounds reasonable.
The problem with handbrake is the ancient, poorly described interface. You have to be a techie and tinkerer to use it. You definitely sound like a techie so you should be fine with time. Lots of guides available, that's how I learned it.
At 1920x1080 and default quality a 2.5GB file = a ~2.5 hour movie. Is that right?
Your PC is faster than mine, I'm guessing you have a good video card too? I have a 1080 video card and use GPU acceleration. Suggest you check that handbrake is configured to use the GPU acceleration (I think it does by default, but not sure).
I'm running a test now all the same settings but the video quality slider set to 0 "lossless". The estimate is saying it will take about 80 minutes, and they "warn" the file size will be the same as the source so we'll see. It's looking like I might have to eat some crow though! Maybe things have been fixed since I last tried it. FWIW I'm only interested in a bit perfect conversion. I just want to get it into mkv format to make playback easier than the native BD structure but I don't want to lose ANY quality and I don't care about file size as long as it's close to the original size. I'll report back with the results.
I learned something, I didn't realize you could go to zero .... so that's where your lossless come from. Cool! It makes sense that the final file would be close to the original - basically you are just changing container formats.
No eating crow - this is how we all learn and benefit from sharing info. Because handbrake has worked for me and YIFY uses it, I've never bothered looking at alternatives. There's probably newer, better programs out there.
Have a look at HEVC/H265. I understand it's much better quality than H264. I can't use 265 as my Western Digital player doesn't support it, but I'm currently building a HTPC with Plex, so that problem will go away.