Is it considered better to have your thumb straight when holding the pick or bent? I know its better to do what ''feels right'' but for me nothing really feels right so i was interested in what would be more efficient.
i cant tell you what to do but i can tell you just do it and dont worry about where you thumb is and it will fall in place
i use streight btw
i use very bent, it's easier for me to do harmonics
but just do what feels right
"The man that hath no music in himself, nor is not moved with concord of sweet sounds, is fit for treasons, stratagems, and spoils. The motions of his spirit are dull as night, and his affections dark as Erebus. Let no such man be trusted."
I change it up depending on what I am doing. I hold it one way for trem picking and another for sweep picking.
Agile 725 7 string w/Blackouts (new paint too)
Jackson Soloist Professional Standard
Jackson SLSMG With Livewire Metals
Fernandes Tremor 4 string
Peavey 5150 2x12 (new tolex and re-biased)
Peavey TNT 100 1x15
Line 6 Pod XT w/FBV
Misc Junk
I mix it up, i change when doing pinch harmonics and such like mentioned above, and straight when strumming chords.
My thumb is very straight, most people would nearly have to hyper-extend the joint in their thumb to play with their thumb in the position I use. My hands are quite flexilbe, I don't imagine this position would be advisable for most.

I recommend you drop your hand loosely to your side, and notice the position your hand is in. Your thumb and index finger should be touching, or very nearly touching. Place a pick between them. That's your ideal picking hand position.
My name is Tom, feel free to use it.