I don't know about resizing files, it's probably better that the user optimise the files first. If they are photographs being sent, then the user would have some sort of digital camera software that can optimise images pretty easily, or even if scanning images, there should be some optimisation functionality to save the image for a balance of quality and file size (as in Megabytes, not dimensions). Even if the images are being sent e.g. direct from a Smart phone, I'm sure there are 'apps' for optimising such images that the submitter could utilise.
I think for viewing the attachments, in stead of having it attached to the email, you can set that option either under the Form Properties or in the Upload Field properties ( I forget which).
In fact, the default option was clicking the link to the file, and the attachment to the email is only a reasonably recent feature. Logging in as the admin for MF, you should be able to view the attachment from within the browser through the submission record list when you open the submitted record to view, there should be a link to the submitted file attachments.