does iaido consist of only learned forms? is there any originality?

Why my I ask do you want to be original in drawing the sword to cut down an aggressor?

It's like asking if there is any originality in a SWAT team course.

These methods require drilling and adhereadnce to proven life preservation skills. Otherwise, you DIE.

Are you confusing this with kenjutsu, the art of sword play, or kendo, the sportive and ritualised form of sparring with replica katanas.

Kendo and kenjutsu are pretty rigid. You are not learning to fight with them, you are learning a weapons system so yo can use it to fight. Like a soldier learning to use his M4 carbine. You are adapting to the technology to get a job done. More so, kenjutus was taught to regiments of soldiers. Hence the mechanical method of teaching (formation teaching, all right handers).

European fencing, using the sabre is fairly unrestricted. The foil and Epee have restrictions on target areas etc. I say this because this sounds more like your interest.

Iai comprises af authentic tried and tested techniques of drawing the sword, counter attack and defense. It has been formalised (Kata) each with a specific scenario always ending with a sheathed sword. Iai stems from the oldest martial traditions of Japan (emerging around 500 years ago) and is the ONLY feasibly training method as the techniques are occaisionally practiced with a live blade and all are lethal - so 'improvisation' isn't part of this art...

Disclaimer: Iaido is a very broad term which cannot truly be spoken definitively of in broad terms. These comments reflect my experience within the Muso Jikiden Eishin Ryu Seitokai. You're results may vary.

Don't misunderstand. Iaido is more than the collection of it's waza. The waza are a training tool used to instill certain patterns of movement into the practitioners muscle memory. In training, you follow the same patterns over and over again. This makes proper technique second nature.

Further into the training curriculum you will be introduced to variations(kaewaza). These will begin the process of breaking you out of the mold you were so carefullly shoved into. You will also be introduced to two man forms which will further expand your understanding of distance and timing.

Ultimately the goal is to reach a point where you take the basic techniques
(how to cut diagonally, how to change directions and maintain a stable base, how to generate proper power with the hips, etc.) etc, and rearrange them to meet the situation at hand.

Still that's the ultimate goal and can take decades to reach. In the meantime, you will do the waza the way your instructor does the waza, and you will think about that waza as an actual confrontation. And that's the way it is.

You can make up all the stuff you want, but that's all those techniques will ever be. Make believe.