Customizing styles

I am trying to ascertain as to how can I roundify tree nodes and control their opacity and add some of the gradients styles - but i fail to see it happening : its not very customizable - I changed node-renderer-default.scss to have following - `rowContents {
@extend %rowItem;
position: relative;
height: 100%;
border: solid #BBB 1px;
border-left: none;
box-shadow: 0 2px 2px -2px;
padding: 0 5px 0 10px;
border-radius: 2px;
min-width: 230px;
flex: 1 0 auto;
display: flex;
align-items: center;
justify-content: space-between;
background-color: white;
border-bottom-right-radius:15px;
border-top-right-radius:15px
}
`

But this is just me - I have forked to customize, but I would like to know if there's already an option to provide style parameters to the tree other than node-renderer - thanks.

PS - I began learning react just a few weeks back so pardon my obvious ignorance...