Which is more appropriate or more commonly used? Toggle switch labels on its right or on its left?
Labels on either side serve different purposes.
In reading order,
Labels before the switch (on the left or top for LTR languages) indicate what the switch is for.
Labels after the switch (on the right or bottom for LTR) optionally indicate the state of the switch.
Here's an example from Windows 10:
When you can't afford space, you can wrap the items without affecting the left-to-right-top-to-bottom reading order, as you see with the first 'Notifications' section of switches in the image above.
Windows 8 mobile also follows this approach, but wraps the state text to a new line for lack of space to the right of the button.
The opposite conventions would be applicable for a RTL language.
In English, I have almost always seen the Label, followed by the Toggle switch. I'm not sure if this would be the same in interfaces using languages that are not read left to right.
Its really vary upon different languages like LTR and RTL format Two kind of writing and reading format used : LTR(Left to Right) and RTL(right to left). Urdu/Arabic and Hebrew letter are RTL apart form that worlds all languages are going under LRT.
These above things are not main concern actually the concern things is about Cognitive Science and our mind set. you can see the example bellow two same page but in different language (English and Hebrew)
I can convey my communication in three language and all are from LTR, so its hard to set my mind to see the things from RTL. if you working for LTR languages like English then, i will suggest to better use right toggle switch