Yes, I highly recommend that you create your sequence from the clip. It ensures that everything matches. However, if you drop a clip on a new sequence, Premiere Pro will tell you that they don't match and give you the opportunity to change the sequence settings. You only get that one chance. Either way is fine.
I found this info on the Video uploading page:
So, since Vimeo recommends higher than 5Mb/s for 720p and even higher for those of us who pay extra to put 1080p on Vimeo, I might suggest that you use the Vimeo preset and then change the bit rate. Take it to 10Mb/s if you are exporting 720p - and if you are not paying for 1080p then don't export that way. Just export to 720p because then you have the control over how it looks rather than have Vimeo shrink it for you.
I pay extra because I like to play my videos via my Roku on my HDTV. In your case, you will have to make the decision. Is it worth it? Or is 720p good enough. Will people be playing it on 1080p screens and forget to turn scaling off? If so, pay extra. If not, why bother?
Now that I have done this research I have to wonder what Adobe was thinking when they chose 5Mb/s for HD.