I am constantly switching my weapons and spellslots, though the shield and inspire hate(that mass madness one) remain always. I am also trying not to hoard items, sometimes using stuff like slow time or that putrid acid just for the heck of it.
Shield and hate are awesome, but I saved them for mass battles. Both have their mana cost lower later on, but hate still eats quite a bit.
The thing I found is if you use em too much the game becomes a cake walk. I guess that is what boils down to my continued use of LB. I wound up getting so may slow times before I found the forge they would have made the game even easier.
BTW are you aiming to find all the secrets? If you are make use of the short load times and keep check secret total after finding each one. I ran into a problem with the PSX version where I triggered every one, but not all got counted, which given the loads times I didn't notice not checking the total often.
Also keep an eye out for the werewolve ruins (Hint: You can find them after you get Mist form). They're a nice challnage compared to the rest of the game.
Power tripping like Kain is a good choice of words to describe the whole game.
Although LoK and the first Souil Reaver were made by different poeple they share the same spirit of design. One part of it is integrating the story with the "feel" of the game and expressing it through gameplay.
In LoK you're reveling in the power you're given and keep being given that plays out through the story where Kain's snobbish aristocratic attitude gets inflated and his reaction to later story twists is fury rather than introspection and humility. In Soul Reaver it's more overt where the shifting between worlds and other gameplay elements tie together to really put you into the shoes of an unstoppable spirit of vengeance that no matter how many times is defeated can simply shift back into the material world and continue attacking you until it wins. Soul Reaver is the prototype of the modern game where you can't lose, but it works because it explains why you are undefeatable and finds ways of giving you challenges and setbacks without having to rely on death as a defeat mechanic.
In both you don't need much story to explain these things because you are actively living out these aspects of the characters.
That was dropped with SR2. The Soul Reaver becomes a back up weapon, rather than the ultimate one that you struggle to not get hit to keep around while other things are put in simply to unlock new content unrelated to the setting. In SR1 you get the ability to climb after defeating the spider vamps, you get swimming after defeating the aquatic vamps, their abilities you struggle against are then given to you; in SR2 you get different soul reaver attunments after completing ruins that are just there, amusingly retroactively explained to have been built specifically for Raziel to complete by the Ancient Vampires that becomes more concrete than a simple prophecy later on.