You can set resizing options in the image upload settings.
You wont be able to show a preview of the picture, that would only be able to happen after the image is uploaded.
In the email settings, you will need to configure the attachment options to have the image attached to the email.
Select the Entered value option, then click the lightning bolt and select the WA Uploaded Files -> Server directory binding. copy the code that this produces then click the lightning bolt again, and select he WA Uploaded Files -> Server File Name. after this binding is added, paste the server directory code in front of it.