How draw electrical drawings?

Hope this is the right place for this questions:

1. When making drawings that use symbology such as
electrical schematics for PLC and control circuits.....
what SIZE should thee symbols be drawn at

2. Should the symbols be in model space and all text
labels be in pspace? Or everything in mspace?

3. Can one draw the WHOLE circuit in mspace and then
cut up the diagram to separate sheets using layouts in
pspace?

Bottom line.... what proper procedure for such symbolic
type drawings?
.