I'm looking at my library and I'm wondering if I should process some of it to reduce the size of some files.

There are some movies in 720p that are 1.6~1.9GB each. And then there are some at the same resolution but are 2.5GB.
I even have some in 1080p which are just 2GB.
I only have two movies in 4k, one is 3.4GB and the other is 36.2GB (can't really tell the detail difference since I don't have 4k displays)

And then there's an anime I have twice at the same resolution, one set of files are around 669~671MB, the other set 191 each (although in this the quality is kind of noticeable while playing them, as opposed to the other files I extract some frames)

What would you do? what's your target size for movies and series? What bitrate do you go for in which codec?

Not sure if it's kind of blasphemy in here talking about trying to compromise quality for size, hehe, but I don't know where to ask this. I was planning on using these settings in ffmpeg, what do you think?
I tried it in an anime at 1080p, from 670MB to 570MB, and I wasn't able to tell the difference in quality extracting a frame form the input and the output.
ffmpeg -y -threads 4 -init_hw_device cuda=cu:0 -filter_hw_device cu -hwaccel cuda -i './01.mp4' -c:v h264_nvenc -preset:v p7 -profile:v main -level:v 4.0 -vf "hwupload_cuda,scale_cuda=format=yuv420p" -rc:v vbr -cq:v 26 -rc-lookahead:v 32 -b:v 0