Any way to increase width of sharing buttons?

If you do not want to enable the full width setting, the first place to look is the “Button Padding” setting, which will increase the padding on the buttons. For further control, like if you want to increase the width, but not the height of the buttons, I would suggest adding some CSS to your site, either directly to your theme or by using the Additional CSS panel, and define your own padding for the .scriptlesssocialsharing__buttons a.button class (that is the class if you are using Flexbox for the “Button Container CSS” option–if not, use your browser’s dev tools to check what class you may want instead).

Ok thanks much! Is there any guide to use custom buttons?

Here’s a tutorial with code to add a Facebook Messenger button as an example. You can add any kind of button you like–they all follow similar patterns.