I'm also in the camp of do it if it's so easy. Sitemaps are far superior to meta keywords because they're an actual technical specification of a quantifiable thing (image, page, etc.) versus a subjective listing like meta keywords.

Haivng easily and readily indexed images can also help with your backlink profile. XKCD has a great example of allowing for such promotion here: https://xkcd.com/license.html  Obviously his content is more likely to be shared, but even in your case if it's a little help it's still help and is unlikely to hurt. Cheers!

Hi Eric. I'd recommend using folders as being navigational and/or site-section specific. As such, they can be shorter--like the two letter abbreviation for states--and create less worries about URL length that way. A ton of other signals are going to be contributing to a page being recognized as being about a resort in Florida than FL vs Florida in the URL alone.

Once you have your structure figured out, using hyphenated URLs that often mimic the title tag of the page is generally a best practice as this gives the user the best idea of what a link is about while also containing keywords when someone links to the page solely via URL.  The Moz blog has plenty of examples such as: http://moz.com/blog/how-to-stop-spam-bots-from-ruining-your-analytics-referral-data.. Short domain, short folder name, then the content. Each bit is readable and understandable as to why it's there.

See: http://moz.com/learn/seo/url for more.  Cheers!

Hi James! This type of URL rewriting is a best practice when it comes to presenting visitors with easy to read page descriptions so whatever capacity you can apply it would be great. Here's Moz's guide to URLs which goes over your question as well as further details into URL structures: https://moz.com/learn/seo/url

Also note from that page:

In addition to the issues of brevity and clarity, it's also important to keep URLs limited to as few dynamic parameters as possible. A dynamic parameter is a part of the URL that provides data to a database so the proper records can be retrieved, i.e. n=3031001, v=glance, categoryid=145, etc.

Note that in both the Amazon and Canon URLs, the dynamic parameters number three or more. In an ideal site, there should never be more than two. Search engineer representatives have confirmed on numerous occasions that URLs with more than two dynamic parameters may not be spidered unless they are perceived as significantly important (i.e., have many, many other links pointing to them).

Cheers!

Hi Georgina. This could definitely have an impact but since it's a more minimal change (root domain is remaining the same) hopefully it will be mitigated (or very minimal) since the 301 redirect was used.  Something else you can do though is go to Google Webmaster Tools, verify ownership of both the www and non-www and set the non-www as your preferred domain within that tool.  The same can be done within Bing as well. In addition you can update your sitemaps by uploading them there so that they include the non-www links as the target pages.  This should help speed things up and make the change over less pronounced. Cheers!

You can submit sitemaps as often as you like to Google Search Console. Many large scale sites would even be doing so multiple times a day as they publish new articles, add or remove new products, and so on. For example, News Sites have a high touch need for fast crawling (hence AMP and specialized sitemap methodologies) Here's Google's help article on this: https://support.google.com/news/publisher/answer/40392

Here's the more generalized version of Sitemap recommendations: https://support.google.com/webmasters/answer/75712

Hi David. The benefits associated with 301 redirection come from either relocating your site, combining sites, cleaning up 404 pages, aligning page names within your site architecture, things of that nature. If you have links or visits to those third level pages and want to house all pages on your root domain instead of third levels, then 301 redirection would be the way to go. Cheers!

Hi Rena. Yes, if both sites are separate domains that you want to use in different ways, then you should place a different robots.txt file in each domain root so that they're accessible at xyz.com/robots.txt and abc.com/robots.txt.  Cheers!