Cersei Lannister’s interest in power is a means of negotiating the world as a battleground. She does not have weapons, she inhabits a battlefield (both court and womanhood), she fights. She fights unstrategically, impulsively, viciously. Her actions re. power are not about setting a long-term plan; they are about self-preservation of her and hers (where ‘hers’ are those she thinks of as offshoots of her actual body, namely her children and Jaime), with a bonus of inflicting maximum damage to anyone who isn’t her and hers. And proving that she’s good at it, good at winning. When she is good at it, it’s a pleasure.
Jaime Lannister’s disinterest in power is because he can put on armor and take a solid whack at everyone who wants to fight him. Notably, on the field, he isn’t a general. We never see Jaime worrying about his troops, or anyone on the battlefield with him. His desire in and approach to the fight are simple; he wants to survive the fight and inflict maximum damage to his opponents. He wants to come out looking a) alive and b) good. He wants the glory and clarity of winning. Because he is perfectly, selfishly, individually good at it, it’s a pleasure.
Cersei’s battlefield isn’t temporary and her sword isn’t physical, but they have the same approach. They are not strategists; they are hotheads. Their pleasure in the fight is in fighting for the sake of fighting. They are given the same language re. catharsis in fight, and when they are unable to fight, they each suffer crises of identity.
Pissing about differentiating the battlefields is skipping the language, ignoring the characters’ actual state of minds, and missing the point altogether.
P.S. Tyrion’s in this, too: fighting with his brain because he can’t fight with his body. The Lannister relationship with power is simple: it’s about taking the most you can get with the maximum force you have. Of course they all have different methodologies; they have different strengths as established externally. Jaime’s force is physical, Tyrion’s mental, Cersei’s courtly/sexual—because that is what the world has allotted each of them. Jaime thinks about power the least because he is required to the least. Tyrion apologizes for his power grabs the most because he’s been the most ostracized by the family. Cersei goes for the power jugular because she’s been directly denied by the world, but knows she is an equal to the family (knows she is specifically equal to Jaime). They are all facets of the same force, Tyrion at a slight remove because he’s grown up at a slight remove, but the narrative drive is all of theirs and the vocabulary is directly shared by Jaime and Cersei. Trying to moralize any of them above the other is a fool’s errand.