What's the difference between a launch tower and a strongback?
Strongback is a part of TEL (Transporter Erector Launcher) that facilitates horizontal transport from horizontal Vehicle Assembly Building to the launch site, erecting the launch vehicle vertically, and holding umbilical connectors for launch vehicle fueling, power and purging gas. On its own, it doesn't enable crew or service personnel access to the launch vehicle's payload once it's erect, albeit it might be used together with a launch tower (like e.g. Soyuz-TMA do). Launch tower on the other hand never supports the launch vehicle horizontally. It is either transported to it with a TEL, or the whole launch platform is mobile, fixed to the launch pad, and the vehicle is assembled in a vertical Vehicle Assembly Building.