>I was wondering What exactly Crashing of Waves does and Also
>Trapping beneath the Thunder.

Crashing: When someone wielding a weapon parries one of your attacks, there is a chance based on your strengths that you may disarm them. If you are unable to disarm them, they may take some damage.

Trapping: If the weapon you're trying to hit with is heavy, you'll do extra damage and be harder to parry with it. This is on a sliding scale depending on how heavy the weapon is.

>Does crashing do anything besides disarming?

Not really, except as described above.

>Is there a
>minimum weight when Trapping ceases to work correctly?

Yes. There are also a lot of weights in which it's not doing very much.

>Also
>would it be better to use Fist of the Titan over crashing,

Judgement call, really.

>Wouldn't that make me able to dual wield a heavier offhand
>weapon

In theory, sure -- but that's assuming you'll always have the opportunity to swap in a weapon that's exactly that much heavier that otherwise is as good for what you're doing in terms of average, material, damage type, etc.

It does give you more options.

>making me do more damage with Trapping or would
>Crashing enable me to land more strikes?

Also a judgement call / situational.