Applying a transform to things overrides the existing settings. You can combine transforms with different effects and settings to get the desired position, effects, etc.
For example
show Sylvie at center, SunsetLighting
Will move the Slyvie image to the center of the screen and apply the shader effect from this pack called SunsetLighting. Hopefully that helps!
Also, if you want a wide array of stage based position presets, check out my staging pack over here: https://makevisualnovels.itch.io/make-visual-novels-sep
It adds a number of new position and camera presets that takes advantage of RenPy's 3D stage, giving you a ton of options for composing your scenes