Hi Alan,
As mentioned by Eric, using chrome dev tools is good for responsive preview. Even using chrome dev tools will open the link in new browser window because its not an actual mobile device. In actual mobile device this will open in new window of your phone’s browser, if you want to open the link in same browser window then you should change this behaviour by manipulating link button html. You should change the target attribute to be _self ( target=" _self "). You can use Set Attribute widget from app store to do this. By default target attribute is set to ‘_blank’ which means it to open links in new window.
Hope this helps!
I like to use Chrome’s device mode for testing, since it allows you to look at your app at multiple sizes: https://developers.google.com/web/tools/chrome-devtools/device-mode/