You should hold the pick in such a way that suits you. If you're comfortable with the way you currently hold it, then stick to it. There may come a point in the future when you want to play faster, or improve your technique, and you may have to change it then. But for now, if it ain't broken, don't fix it.
My Current Gear
Gibson Les Paul Standard Faded (Cherry Burst) || Gibson Les Paul Junior (Vintage Sunburst)
Marshall 1987X and 1960AX || Weber Mass 100
Fulltone OCD pedal || Ibanez TS-9 tube screamer || Big Muff Pi with Tone Wicker || Boss AC2
I forgot to mention that sometimes I get pain in my thumb in the joint I think it maybe because I have my thumb pushed inward but that's why I'm asking here
personally i hold the pick with the last nuckle of my index finger in the center of the pick so i always know where the point of the pick is at. when im strumming chords or need to have less attack, i have the tip of my thumb in the middle of the pick but when im doing riffs that require more attack or i slide my thumb forward to get more force behind it. but what they are saying i agree with find what works for you. try a whole bunch of different things and find something that suits you.