forms - Having two different label alignments in one website / application

I've come to learn that label alignments have their purposes: top-aligned / right-aligned for faster completion (usually for forms asking common information) while left-aligned for slowing down completion (like advanced settings or those forms where you require users to be more cautious in filling out the form).

My question is, is it okay to have two different form alignments in one website if those two forms have different purposes? Or is consistency / faster completion rate more important (so it's best to just stick with right / top aligned labels and never bother with left-aligned labels)?

Answer

Yes, if there is a good reason to have two different style forms.

Remember that you should break any UX guideline when you have a good reason to. Consistency is one of those, but it is one that you should look at carefully before breaking it.

The biggest test is going to be whether users find it odd or problematic. Make your decision primarily from what you learn in your user testing.

Edit: As an example, take a look at the way that gmail handles forms. For the sign in form, they use a top alignment, but for the settings form they use a left alignment. I've never heard of anyone complaining that this confuses them, as each form has a clearly different purpose (as the op was asking).