Thank you.

Correct, the potions you created in Oblivion only had the effects from its ingredients that you knew at the time you created it. Said potions don’t gain those effects once you know them, but the same recipe will add new effects once you learn them, and thus you might need a different recipe to make the potion you’re trying to create.

You'd have to eat the raw ingredients. Drinking potions doesn't level it up AFAIK.

You may have a mod that included the "shut-the-fuck-up-nirn-root" mod (cant remember name) or a sane dev lowered the base volume of that Audio effect in one of the many ports/remasters.

Or you legit never stumbled across it. You will 100% know if you stumbled across it.

People complained about the sound!? I guess it could be considered annoying, but they're rare, non-respawning items! Once you pick it, you never have to listen to it in that location again...

It's time to see the doctor

thats fucking weird man. the sound is very distinct and pretty loud

The easiest one I know where it is, is just outside Lakeview Manor. Exit, take the path/road to the left/ East-South-East towards Pinewatch. There is a pool of water at the edge of Pinewatch's land with two mud crabs and a nirnroot. Go there and you'll hear this

The white and pink monster also have a 10% chance of causing gender dysphoria