You might not notice or care about compression artifacts as much as me, in which case you can go for a lower quality setting and save more space. My advice would be to try things out for yourself, to see what works for you. Also I routinely get file sizes down to like 1/3 of the original file. The settings I use generally result in really good video quality, and only the loss of very fine detail that is hard to notice to begin with, and becomes doubly so considering the image is in motion and I don't watch my compressed files on my big TV, only my monitors or tablet. And that's down to the settings you use to compress it (and partly how well you can spot compression artifacts). The important bit is whether or not you notice it. That being said, lossy encoding doesn't always incur noticeable quality losses. The Blu-ray, however, is encoded using lossy compression, so it is still lossy to lossy. Makemkv rips are lossless with respect to the Blu-ray. I have used hardware encoding for 4K re-encodes, but I've mostly left those uncompressed lately. I've found that CPU encoding is still king at this point. I'm hoping we see a slower preset that gives us better PQ. I don't begrudge anyone who likes using hardware encoding, but it's not for me right now. I don't use the nvidia, Intel, or AMD hardware encoding because, in my opinion, they either lower picture quality or make the file larger than I talked about above. You will need to do some test encodes to figure out what works best. Anything over 24 really wrecks the grain pattern on old films. In my experience, anything under 18 CRF has had a negligible difference in PQ. The more bits you allow for the encode, the more fine detail you will get. Most of the default settings are really well tuned. There are a million different encoding apps out there, but I've been using FastFlix for quite a while and find it's a nice balance of good settings out of the box yet still allowing you to turn the knobs if you need to. I re-encode most films that have grain with the grain preset at 22-24 setting for picture quality. Use a lower CRF to get better quality (more bits). I use the default preset at 18-20 setting for picture quality (CRF). If you are re-encoding digitally shot movies without any added grain or special filters that can increase the complexity of the image, you should get nearly 1:1 picture quality around 5-8GB file size. Now I try to match the picture quality as close as I can to the original. I used to try and go as low as possible with lossless audio.

I have converted at least 2000 of my Blu-Rays to h.265.

Makemkv 4k bluray