I cook rice without a rice cooker all the time, and some of the tips you're getting seem dubious to me. Rice is pretty forgiving though, so maybe those recipes work, but I do it a bit different.

I treat all species of rice exactly the same, and they all come out perfect. Short/medium grain rice comes out just sticky enough so you can grab chunks of it with chopsticks, long grain rice comes out beautifully fluffy, no stickage, with all the grains nicely separated.

I use a 1:1 rice to water ratio, plus an extra quarter cup of water. That bit is important - the extra quarter cup is what evaporates off and escapes as it boils/simmers, the rest is absorbed into the rice. Doesn't matter if I'm cooking one cup of rice or ten, I use an equal amount of water plus a quarter cup.

I bring the water to a boil first, then dump the rice in. Wash it or don't - I usually don't, and the difference is slight. Once the rice is in, I turn it down to a simmer, put a kitchen towel over the pot, then squish the lid down over the towel, onto the pot. The towel helps make a better seal to trap more of the steam, but without the danger of making a pressure bomb. The towel also prevents condensation from collecting on the lid and dripping into the rice, which can make it soggy towards the end of the cook. I simmer it for 20 minutes, turn off the heat, then let it rest for another 20, with the lid still on. Leave the lid on until after it's rested, or else some steam will escape and your rice might end up "al dente". Once it's rested, take the lid off and stir it to fluff it up a bit, and you're golden.

I've been making it that way for years with several different kinds of rice, and it's worked like a charm for all of em.