[Erik Rakovsky]

Except for uncompressed video there is no such thing as “lossless”. All codecs are lossy.

These two things simply aren’t true.
You can have compressed video which will be truly losless. Even if you only zip the data stream.
There is a list of lossless codecs for video (and it is pretty incomplete) and as you can see, even h264 has lossless mode (in I444 colorspace, however, and what is worse, this option is not readable by Vegas):

https://en.wikipedia.org/wiki/List_of_codecs#Lossless_video_compression

What is even better: YouTube accept lossless h264 (I tried it) and for some sources (256 color graphics, some computer generated scenes e.g. in games – because there practically isn’t any noise) the bitrate is not so catastrophic
OBS Studio with nVidia graphic cards can directly encode to the lossless h.264 using hardware encoder NVENC – when using AverMedia LGP2 (1080p30/1080p60, I420 colorspace expanded to 4:4:4) I obtained mostly around 50 Mbit/s, what is less than bitrate of Avid DNxHD or Cineform, which are both lossy (much less, DNxHD is going up to 145 Mbit/s and still is lossy)

However it is possible to make final render into h264 lossless: you can use Debugmode frameserver and feed the data into x264 encoder (maybe after doing colorspace expansion and conversion in AviSynth or maybe it is even possible in x264, I didn’t know).