I'm not sure if it's always possible to alter the copy properties in various apps (I don't recall seeing such options in prefs), but in case this won't work in the situations you'd like it to, I'd recommend
Plain Clip (freeware). I've been using this utility for years to strip formatting from text on the clipboard. You drag its icon to the dock, and click on it
after you copy and
before you paste. More filter options can be accessed via its prefs.
Again, I'm not sure if you can change a browser's page display details relative to the loading process. You can, however, stop various page elements from showing/downloading until you know you actually want them. There are adblockers like Adblock Plus (see Firefox Add-ons or Safari Extensions). In addition, Safari has a pair of great extensions that block flash or other items requiring plugins for display:
ClickToFlash and ClickToPlugin, allowing you to manually click them back on. (Btw, any reason you're not using Safari?)
Likewise, I don't think you can control QT's display relative to the download status of a clip. Contrary to yours, my experience is that QT starts playing well before a clip has come in completely, as judged by the progress bar below the video window.
Finally, you can toggle Firefox's Downloads window on and off in its General preferences panel, but I haven't checked v7. AFAIK, Safari won't allow that (at least up to v.5.0.6), but there may be an extension that does the trick.
