Is it faster for m241 to execute logic in pou or execute logic from library?

[tst]

Good day to everyone 😁. I have 4 pcs of m241 plc which 90% of the code is same. These common code consists of FB call, read write register (%MW, %MD), CSV files generation based on logic and web visualizations.

Previously, I write the code into 4 different project files for each of the m241. But when there are changes to the common code, I will have to modify the them 4 times. 

Thus, I created a library file to store the common code. When there are changes, I only need to modify the code once. 

And now I have a few questions:
1. Which is more cpu load friendly? Running logic in pou itself or running logic in library (trigger from pou)?

2. Is it common to write logics and executions based on input in library file?

3. What is the normal way to code when you have a few plc running with the same code? Same pou in individual plc or put them in a library file? Or just put FB into library file but logic still run in pou?