The user icon from mobile can be replaced with another Fontawesome icon with custom css.

The css is the existing custom css for the icon.

.fa-cogs:before {
content: "\f085"!important;
}

Replace the icon code f085  with the new one from  https://fontawesome.com/icons

Since Redux framework cannot save the \ from the css, the new css needs to be added in Customer or in style.css from Child Theme.