What recipe where you’re cooking can you change ingredients by such extreme amounts?

some examples:

• chilli has lots of leeway in the amount of chillis, beans and meat, and seasoning.
• when I make potatoes with sauce and meat, I can add 50% potatoes and reduce meat by 50% and it’s still good (albeit less meat).
• frenchfries with very little salt is good

generally my exact compositions depends of packages sizes and what is available, and how cheap I am. i.e I usually put full cans in it, and thus round to the next full can. And when I want to save money, I put half as much meat in it)

Pasta bolognese or lasagne with 2x as much meat and a quarter as much pasta would be all wrong

80% meat lasagna sounds awesome.

Balance the amount of butter with the amount of flour?

That is something that needs to balanced, but even then I am ±20% i guess.

When you cook rice, do you experiment with different amounts of water?

Rice is the one thing that needs exact measuring for water.

Or do you just cook it until it’s cooked?

I know someone who cooks rice like pasta, i.e. with lots of water, and in the end uses a sieve for the excess water. I may be crazy, but I am not that crazy.