Ok, FINALLY found what I needed. It seems JWPlayer (which is awesome btw) has a Cloud Hosted version, and sort of an advanced Cloud Hosted version. With the easy version, one simply includes:
<script src="//content.jwplatform.com/players/<CUSTOM VIDEO ID>.js"></script>
where they want the video to appear. For the advanced version, the player code is inserted into the head tag, and then additional "overrides" can be implemented.
<head>
...
...
<script src="//content.jwplatform.com/libraries/<CUSTOM PLAYER ID.js"> </script>
...
</head>
<body>
...
...
<div id="jwAerialVideo"></div>
<script type="text/JavaScript">
var playerInstance = jwplayer("jwAerialVideo");
playerInstance.setup({
//Placeholder Image
image: "//content.jwplatform.com/thumbs/<CUSTOM IMAGE ID>.jpg",
sources: [{
file: "//content.jwplatform.com/videos/<CUSTOM VIDEO ID>.mp4",
label: "360p SD"
},{
file: "//content.jwplatform.com/videos/<CUSTOM VIDEO ID>.mp4",
label: "720p HD",
"default": "true"
},{
file: "//content.jwplatform.com/videos/<CUSTOM VIDEO ID>.mp4",
label: "1280p HD"
}]
});
</script>
...
</body>
This allows for me to specify a custom placeholder image and set the default video quality to 720px.
The two articles used to as references to do this are Here and Here
NOTE: One thing in their instructions that is not correct anymore is that to find the custom video ID's for each quality of video, in the dashboard go to Content-->Videos-->Select your video-->Sources Tab. This as of JWPlayer 7.