FX TD (Effects technical director)
FX TD generates digital effects such as, explosions, fire, smoke and water in 3D software, who works under the management of the visual effects supervisor. They are in charge of supervising the particle and fluid effects for VFX sequences. FX TD
FX TD needs to understand how to manipulate particle or fluid systems. Many effects require FX TD to have the ability of programming to go beyond the base setups and to create more complex FX system.
This article on LinkedIn tells more about this job role, what skills and qualifications does a FX TD need to have, and the specific responsibilities.
https://www.linkedin.com/pulse/what-does-fx-technical-director-do-entertainment-industry-bisbey
Some examples can be found in Franco Pizzani’s works, who works as a FX TD in Vancouver.
TD (Assistant technical director)
They assist other TDs in the pipeline, provide technical advice and support for artists, and get information of each department on the needs. Assistant technical director will work closely between software developers and other artists. They also need to manage data information such as, disk usage, file transfers, converting and resizing files.
The following job post of this position from DNEG studio describes what this role is like. This position will gain the opportunity to focus on the specialised field as a Pipeline TD and experience the leadership role. In this job post, TDs are also required to have strong Python scripting skills.

Software Developer
They use programming skills to build systems for technical directors (TD) to use and modify, so that TDs can meet their specific needs in VFX projects. Their responsibilities are developing and maintaining software as well as integrating tools into the existing pipeline. I found that most VFX companies require this job role to be capable with Python scripting.
Some evidence can be found in these companies:
1. DNEG
Full link: https://jobs.jobvite.com/double-negative-visual-effects/job/owHw7fwA

2.MPC

Pipeline TD (Pipeline technical director)
Pipeline TDs make sure that every studio member has the tools they need to complete the shots, and if not, they need to code them. Pipeline TDs should alway be ready to solve the technical issues to ensure a VFX project runs as smoothly as possible. They need to be highly knowledgeable in providing software solutions as the problems arise.

