How, as a Pathfinder DM, can I help my players create characters at the correct optimization level for a given adventure?

My D&D 4e party is a few levels away from the end of their epic campaign, and they want to keep playing D&D with me.

I have recently discovered that I really like some of the Adventure Paths for Pathfinder and we already decided that we will be switching systems, but my current players either started with 4e (3 players out of 4) or never created the mechanical part of the character themselves.

One big difference between the system they already know (4e) and the one they need to learn (PF) is that once you understand that hitting often is important and dealing more damage, raising defenses and winning initiative are the next steps, 4E characters are easy to build. Building powerful PF charcters requires way more mastery, despite the availability of SRDs there’s no electronic character builder that helps you filter feats and powers you can take and trap options are many more and harder to spot.

So, building an optimized character is hard – and I think building a character that is balanced against the campaign is even harder. The one Adventure Path I’m currently DMing, Curse of the Crimson Throne, seems to be written with the assumption that random guys who just met at a Pathfinder Society organized play table should be able to play through it with no hassle.

For comparison, at my table even a Swashbuckler (a tier 5 class, which according to the tier system means “not the best even at its main job”) is dishing a lot of damage around. Three level 10 characters (one level lower than the AP mandates) dispatched an Advanced (32 more HP and more AC) version of Cindermaw in one round just by dealing enough damage.

(We had one alchemist with frost bombs, one swashbuckler and one investigator with a firearm)

I’m wondering if limiting available material to Pathfinder Society approved material, or limiting material similarly to 5e’s “core + one book” limit, maybe combined with “no tier 1 or tier 2 classes”, could be enough to creat characters who get properly challenged in combat.

If such easy and formulaic methods are not enough, how does one ensure that the characters are at the right level of optimization?

Unless we change our mind, this group will be playing either Way of the Wicked or Curse of the Crimson Throne.

To me, D&D/PF adventures should provide interesting encounters, both of the social, of the explortation and of the combat type.

I define a combat encounter interesting when the players don’t just repeat the same motions and each fight becomes some uninteresting loss of time because they would have won anyway. Combat has to be enough challenging that players feel smart because of their approach, including doing some research when possible (i.e. combat as war).