Personally, I don't like writing everything in a single procedure. Instead, I write procedures according to their need and follow these standard rules for any basic table.

Take for an example of mstEmployees table, for this table I will create procedures for GET (usp_mst_GetEmployeeByID), GET ALL (usp_mst_GetEmployees) & SAVE (usp_mst_SaveEmployee) employees.

And regarding error & transaction handling, you really don't need that in these type of procedures, as the GET/GET ALL methods are just plain SELECTs and SAVE method is either INSERT or UPDATE (only 1 DML statement).