Piracy: ꜱᴀɪʟ ᴛʜᴇ ʜɪɢʜ ꜱᴇᴀꜱ

In most cases, most release groups already fine tune encoding settings towards various balances of file size and quality, so the best option is to decide on a set of release group whose standards meet your needs and just use the files as they come without further modification.

Applying lossy compression to a video that's already had lossy compression applied to it degrades it unnecessarily, so if you're going to compress it yourself, it's best to start with the remux, aka the original media file.

I'd personally recommend releases from members of the qxr group and Vyndros.

Don’t encode lossy to lossy. The encoding will take forever and the image quality will suffer. If you want file size savings redownload your media in h265 or whatever. Or temporarily download a lossless copy, encode, and delete.

Are you short on disk space? Personally I'd just buy enough storage that I don't even need to care

You need to do 2 pass encoding. You should also not use CRF. You should pick a bitrate for the file size you want. Do a first pass which analyzes the video to see which sections require more data, and then run a second pass which will give high bitrate to more action scenes and lower bitrate to the credits and slower talking scenes.

Some action scenes require 5 times more data to look as good as a talking dinner scene, you couldn't even notice the quality difference but the bitrate requirement is literally 5 times more.

You also need to use the slow preset and use x265 if you're doing this to archive the stuff forever. Do it once and do it right.

I'm confused... Are you grabbing pirated video files from the net and re-encoding them... If you're attempting to further compress already compressed video, you're just zipping a zip file. It's crazy and you'll do nothing but bloat the file size (versus a properly compressed video file) and further reduce the quality of the video via artifacts. I'll call the police and have you committed right now.

If you're grabbing 8/4k or UHD BD movies and re-encoding them into lets say, 1080p HEVC 10bit, I could see that being worth it if you really love the movie (and have 5 days with nothing to do), but only if you're going from an inferior compression to better (h264 to h265), otherwise like I said, you're zipping a zip file.

In my opinion the ideal x265 size/speed/quality is using a tuned slow preset, perhaps with filtering if the source is grainy. A test encode or few should be done to determine an ideal CRF per source.

Since you don't seem very familiar with x265, I would just stick with the defaults in slow preset, but consider using aq-mode 3 or 5 (only available in the patman mod). You can also adjust the aq-strength to help control the resulting size somewhat, I wouldn't go lower than 0.5.