CTE where to place the where clause to filter rows sooner (in postgresql)?

I have function with CTE which looks like this:

function param(p_userId, p_templateId)    with a(select...),         b (select..),          c (insert..returning..),          d (update..returning..),         ...k(select..)    insert ...     select * from k     where  userId = p_userId     and    templateId = p_templateId

I'm able to put the where clause right at the begining in the a CTE. If I place the condition at the end like I have it now, will it filtered the rows out at the earliest or at the latest time? What is faster?

Basically what I do is, in the CTE's which appear sooner, like the a or b, (rather then k), I'm prefetching data or precalculating columns in order to use them later in the following CTEs.

Hope this question is still not too vague.