Usually, the sweep angle is defined at the quarter chord line, and trailing edge sweep then follows from:
- Wing area. Larger wing area means lower wing loading and associated structural weight, higher profile drag.
- Aspect ratio. Higher aspect ratio results in longer span, higher structural weight, and lower induced drag.
- Taper ratio. Higher taper ratio implies lower tip loading.
- Quarter chord sweep angle. Higher sweep has beneficial effects on postponing transsonic shock waves, but detremental ones on stall behaviour and structural weight due to torque.
Seen in this perspective, trailing edge sweep is just a by-product of the four planform-defining entities. It may be desirable to have a straight trailing edge sweep for secondary purposes such as stowing the landing gear, and this may make the design team reconsider the combination of the four main parameters.
The three wing planforms drawn in the OP differ in all four defining parameters. Wing area and taper ratio decrease from up to down, aspect ratio and quarter chord sweep increase.
This article describes the aerodynamic design considerations for transsonic wings, and compares wings with varying sweep and thickness, same area and taper. The middle wing has a trailing edge sweep angle of close to zero, following more or less by coincidence from the definition of the main parameters.