Only considering VXL support material, the higher the temperature, the better, since this will lead to faster dissolution. But the reality is a little more complicated. You need to consider the maximum temperature your model material can handle without deformation. A good rule of thumb for amorphous thermoplastics is to go 30 °C below glass transition temperature of your model material. For semicrystalline thermoplastics it is more difficult, since elevated temperatures might also lead to crystallisation which might also deform your model. For these materials, please see the material suppliers info on heat deflection temperature.
Some examples for maximum dissolution temperatures:
|ABS warp free
|Please check data sheet of supplier and look for glass transition temperature
|45 – 60 °C
|There are low temp and high temp PETGs out there, please check Tg
|80 – 90°C
|There are low temp and high temp PCs out there, please check Tg