Protected App Signals: Signals, Base 64, and maxSize in encodeSignals

[thegreatfatzby]

I'm trying to wrap my head around PAS, I think these questions three are all part of the same misunderstanding I'm having:

1. Are there any limitations to the individual signals that can be stored using the updateSignals call (I see the 10-15 KB limit per owner, I'm more asking per signal, like bit limitations).
2. Why are the signals Base64 encoded? Is that just for the docs or is that a requirement?
3. Who determines the maxSize parameter for encodeSignals, and assuming it's the framework, what is it trying to do and how is it determined? Will this be determined somehow to enforce some privacy constraints?

I guess I'm ultimately trying to wrap my head around what the signals can be, what restrictions on their declaration and use might be in order to maintain privacy, etc.