After a discussion between the group, we've come to an agreement regarding all the buttons/options and the visuals of the Main Menu and the Options Menu.

We chose to use some objects of the type "TextMesh Pro", so we would have more freedom with custom fonts and attractive color.

Regarding the slider for the volume of the game, we changed the handle by just choosing a custom image of our liking.

We also hooked up the slider to a "label" so it would show what percentage the slider was on.

To do that we created the following script that receives the value of the slider as soon as it's changed, then it multiplies the value by 100 and adds the symbol "%" after the value.