Choices, choices.  The designer literally has all of them at some point.  As the design progresses, they dwindle along with flexibility.

When designing a part for Welding, there are times where it becomes necessary to incorporate Filler material into the assembly.  This can be to accommodate manufacturing tolerances, to reduce stress, or to join materials that may not readily weld without an intermediary.

These have to be considered when selecting an appropriate filler.