Both of your descriptions chime with me @PeeGurl74 and @gldenwetgoose. (And both of them are great fun to read, thank you!)
'Letting loose a monster' is a good way of describing it, though I will have generally a pretty good idea of the options open to me. So when the urge strikes I will work out pretty quickly which of the things I have been wanting to try, or that I know work well and give me the thrill, fits the opportunity best.
RIght now I know that when that sudden urge comes, I'll be thinking whether I can pee against the outside of my glass patio doors, while videoing it from inside, or whether I could justify doing a load of washing so I can sit in a garden chair and just wet my clothes for the fun of it.
There will sometimes be a fantasy playing out in my mind, but mostly I'll just be enjoying the thrill of a near-spontaneous naughty pee, the internal physical sensations, and the visual and audible treat of peeing for their own sake.