what if the preexisting venv is just the system python? my base image is python:3.10.10 and i just pip install all requirements in that image. Does that not avoid venv still?

it will basically create a new venv inside the container forking the existing preinistalled stuff (i.e. the new venv already has everything the python system has preinstalled)
then it will call "pip install" on all the "installed packages of the Task.
Which should just check everything is there and install nothing

If you set " CLEARML_AGENT_SKIP_PYTHON_ENV_INSTALL=1" it will do checks and just use the existing system python environment as is.

, I can get 50 tasks to run in the same time it takes to run a single one? i cant imagine the apiserver being a noticeable bottleneck.

50 containers on a single machine would be fine if you have enough RAM/CPU, and yes they would run concurrently.
regrading the time itself, again the spinup time of a Task should be negligible.
Pipeline tasks are not meant to be "threads" they are meant as different functions you want to run on different machines,
This means that if your pipeline is just a set of simple functions that require no cpu/gpu or IO, I'm not sure pipeline steps is the right way to go

Does that make sense?