RSS Feed

Hello I set my RSS feed limit to 100 but am getting complaints that when subscribing by email they are sent 100 emails.

I would like a Feed Reader to load all 100, but when subscribing by email set the limit to 10.’

Is there a code I can use in functions file to achieve this?

Also a side question, I notice sites like verge.com have a thumbnail of their company logo for the RSS feed, for example using google newsstand it shows there logo in the banner of the feed. Any idea how to do this.

Thanks!