I can only tell you what helped me to play by ear (primarily hearing where chord changes are needed as well as what key to play in).
I Initially started by using an Autoharp. The school at which I taught had one just sitting around unused so I figured I’d give it a try.
About a year or so later I began learning guitar. But I was ALWAYS better able to recognize chord patterns when playing the Autoharp as opposed to the guitar. But even with the Autoharp, it took almost all of that first year for me to even begin to hear when chord changes should be occuring.
My personal theory was that it was due to not being distracted by the fingering necessary to form chords on the guitar. That kind of distracted from actively listening for the chord changes and patterns.
So, for your situation, I would assume that whichever method requires the least mental distraction would probably make it easier to focus upon listening for patterns and chord changes.
Like you, I also played an instrument (trumpet) in my childhood but never learned music theory etc.
But can you clarify something in your Q, please.
When you refer to choosing a pick vs. fingers do you mean just strumming with the pick vs. finger picking technique or what? That’s basically what I used the pick for. But I’ve seen some players doing some intricate picking (more commonly on Banjo) with a pick so I’m not clear on what exactly you’re referencing.
Anyhow, I would say to choose whichever method is the bare bones simplest; kind of like it’s easier to initially learn to drive a car with automatic transmission because you’re free to concentrate on driving skills without being distracted by when to shift. Less multitasking.
I hope what I’m trying to say makes sense.