While I'm using Alt+click mechanic to move items between my inv and chests, after 2 or 3 interractions my ping goes up to 1500ms. Never had this issue with 1.16 item scroller, I would like to know if the issue is on my side or from some changes in 1.17.

This may be related to #70. So you can probably also fix the issue for yourself disabling that option. There were definitely inventory related changes in vanilla 1.17, but not really any Item Scroller functionality changes, just stuff adapting to vanilla changes.