Hi ctstrist,
ScrollBar’s change event is fired when the scroll buttons or the scroll thumb is being pressed or dragged accordingly. In order to scroll the content of a container you need to listen to that event and use the value of the ScrollBar to set the scrollTop/scrollLeft of the target container. Here’s a simple example:

<!DOCTYPE html>
<html lang="en">
<!-- references to JS and CSS -->
        #scrollableContainer {
            width: 500px;
            height: 200px;
            border: 1px solid black;
            position: relative;
            overflow: hidden;
        #innerScrollableContainer {
            width: 100%;
        window.onload = function () {
            let scrollBar = document.getElementById('verticalScrollBar'),
                scrollableContainer = document.getElementById('scrollableContainer'),
                innerScrollableContainer = document.getElementById('innerScrollableContainer');
            scrollBar.max = innerScrollableContainer.offsetHeight - scrollableContainer.offsetHeight;
            scrollBar.addEventListener('change', function (event) {
                scrollableContainer.scrollTop = this.value;
 <smart-scroll-bar orientation="vertical" id="verticalScrollBar"></smart-scroll-bar>
 <div id="scrollableContainer">
        <div id="innerScrollableContainer">
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There’s should not be any issues/lagg if done properly. Additionaly if you want to add option to scroll using mouse wheel, you will have to listen to the wheel event on the target container and add your custom logic to change the value of the Scrollbar. The event is standart and well documented in the MDN Web Docs.
Best Regards,
Smart HTML Elements Team