If you are doing digital IC design, you are more related with stand cell, such as those cells in the timing library (*.lib and *.db).
You can not adjust the W/L of the transistor, you
just can select those stand cell with different driving
strength (X2, X4....)
For the analog design, you are facing many transitors. You directly adjust the W and L for different transistor...
For the RF, you just have several transistor to
play with... W/L also can be adjusted.
Hope this help you.
Best Regards,
Tony