When you play a given scale, how do you know what sharps or flats are in it? Do you look it up in a table somewhere, or do you already have some system to remember? Or do you always just read the scale from the page that already has the correct key signature? If you saw a particular key signature, say 4 flats for example, would you know what key that was, and if so, how?
You're right that there are many ways to learn, but the information that ends up in your brain is the same no matter which path you took. I'm just wondering how you manage scales and keys right now using whatever learning method worked for you.
When I was a kid, I first learned all my scales by ear. If the new scale I was learning sounded like the other scale I already knew, then I had it right. I had no idea about keys or flats and sharps. That worked fine until I started reading music in different keys. At that point I had to learn how to tell what key signatures meant and which notes were supposed to be flat or sharp. Without some sort of system, i.e., the circle of 5ths, it would have been extremely difficult for me to memorize that amount of information. I'm just curious how you do it and what learning method has worked best for you.
The way I identify keys is look at the last sharp and raise it one semitone or look at the next to last flat. For example, if the last sharp is D#, one semitone up is E, and that's the key (E). If the next to last flat is Eb (and the last flat is Ab), then the key is Eb. If the key is known, but the key signature is not, then I use the above rules in reverse plus the circle to fill in the blanks. So for the sharps in B, going down a semitone to A#, tells me the final sharp. Going around the circle, I start at F# then C# G# D# and know to stop at A#. For flats, taking Db as an example, I know Db is the next to last flat. I start going around the circle from Bb then Eb Ab Db then add the next flat after that, Gb. Sounds complicated, but I've not come across a simpler way to do it. If I didn't teach my students this as soon as they started learning the different keys, no matter how young or old they were, I'd have failed as a teacher. Any musician who reads music is going to be lost if they don't understand keys.