This is an issue with jquery ui sliders. I googled and found a solution is to include touch punch after your other script includes in the head:
<script src = "https://cdnjs.cloudflare.com/ajax/libs/jqueryui-touch-punch/0.2.3/jquery.ui.touch-punch.min.js"></script>
It depends on "best" as Hype Reflect is the easiest, but may also be the least accurate. Previewing in your project will be the most accurate. Second to that is may be previewing in Mobile Safari depending on your app (as Hype Reflect is a WKWebView in an app, so in some ways this could be better).
Hype Reflect does not handle mailto: links; it is not a problem with the code. IF you use the Safari icon in Hype Reflect and preview in Safari it will work fine. You may need to explicitly handle this in your app, depending on the setup.