Requisites Again - Using lowest score?

When does a spell require that the lowest of arts be used? Always?

It is regardless of cosmetic effect, magnitude etc ?

Spells that list a requisite require the lowest score be used. Spells using multiple forms and/or techniques should list their requisites unless the effect is purely cosmetic.

Yep, you use the lowest regardless of if it adds a magnitude or not, but you don't list a requisite at all if it is a purely cosmetic matter and thus are not limited by them in that case.