Jazz guitar picks or plectrums are usually medium-small and heavy gauge for the quickest response.
Perhaps the easiest pick to use is a thin medium to large one that is easy to hold and with some “give” to prevent it from moving around when held.
Of course the problem with t gauge picks is that they give too much and cause a slight delay and slap-back.
The jazz pick, however, is rigid and although more difficult, especially for the beginner, to hold it produces a response that is immediate when playing fast jazz scales or lines when improvising.
Also, if you tend to lose plectrums I find that brightly coloured picks are harder to lose!
I once had a hundred printed with my name and telephone number on them and most of them were all lost within a few months – they were all black!