Have you looked into ahrefs? I know a ton of horsepower behind it, but don't know if it can handle checking 20m. Good luck!

Logan nailed the answer. Quality over content always. Even if you have good metrics, you may not have a baseline to compare to it yet. One way is hiring an independent contractor to produce 5 or so articles and compare metrics and cost and go from there. It's difficult to do, but you should always be testing! Good luck.

The link from Alick300 is extremelly credible that comes from John Mueller from Google. However, I would look at these 2 links as well:

https://www.rebootonline.com/blog/long-term-outgoing-link-experiment/ (an interesting expirement) https://moz.com/blog/external-linking-good-for-seo-whiteboard-friday (Is External Linking Good For SEO? - Whiteboard Friday)

They both go into some additional details.

I agree with Alick300. As long as the structure make sense and you (typically use) one H1.  Also, you shouldn't go from an h1 to an h3 without an h2.  I can see h3 being more than h2's in a case like below (even though I would use li)::

h1 - heading
   h2 - subheading
      h3 - subheading
      h3 - subheading

If you have access to the main server's configuration file, place there. Code in httpd.conf is compiled on server restart where .htaccess is interpreted on every http request. The best way of doing it.

For long-tail kw positions, generally you will not see a dramatic drop. In fact, many times no drop at all. For some of the more competitive positions, you most likely will see a slight loss.  Some companies do see a dramatic drop--but most likely because of other factors. Over time, expect to regain those positions if you focus on ux.

Dan's comments were spot on. I typically launch early on a saturday morning (2am or so) and make sure everything works. If you do launch, and the site blows up, you can always switch the 'a' record to the old site (assuming it is at a different server) and troubleshoot.

1. Do you think this strategy will work to preserve my current rankings? Yes, as long as the 301's are done properly and expect around a 15% loss.

2. Do you have any lessons learned or advice to share with me to make this as smooth as possible? Make sure to test the 301's before hand. Specifically, change your hosts file to the ip of domain. Next, go to google and do a site:yourdomainname.com and click on each result and make sure the redirects are done properly. Also, pay attention to Google Search Console, Analytics and etc for 404's and such. Make sure your .htaccess file isn't huge and add a new sitemap and etc.

3. Do I really need to wait to add new content?  I might get antsy and want to do it sooner!   No, but I would wait until the dust settles (more of a personal preference)  as you need to focus on the launch.

Sounds like you have it handled! It's all in the prep and how to handle issues post-launch in a time-sensitive matter. Good luck!

Yes, for the most part. Google wants to deliver the best results for visitors based on their search query. So if something is hidden from initial view this would impact ux and especially if it's poorly implemented (not intuitive). As you know, original and compelling copy is the best. Unfortunately in many situations, such as a large ecommerce site, it is resource intensive. It's best to avoid thin content. However, it does get ranked as you can grab a snippet and place in Google and look at the results. So yes, it's possible that Google will rank these pages with duplicate content in a hidden view.

I would advise you to tell your client to remove any hidden content and rewrite product descriptions. Depending on resources, they may/may not want to do this. If they don't, at least you made a recommendation. Good luck!

The Googlebot will crawl this information. However, Google may elect not to index it or discount this content in its rankings.

Don't agree. Many time you have room for your company or branding and it is a good idea. It's an easy way to gain market awareness.  Also, stuffing a ton of kw's in a title can look spammy.

Yes, I typically always do and place it after the topic of the page:

Plagiarism Types | Brand

It helps with brand recognition.  Just remember that if is a long brand name it will get truncated. Also, make sure you have a compelling meta descriptions to improve click-throughs.

Good luck!

Don had a great answer on this. I focus on directories that have some sort of value to the end-user and any site just can't get listed (for the company I work for is industrial B2B). If it doesn't meet these two criteria, it's most likely spammy and not worth getting listed in. I wouldn't get hung up on a set number or a specific pagerank.

I wouldn't change a bit. I always focus on making sure a site is accessible and has an optimal site architecture first. For on-page content, I will create (or attempt to create)  a compelling user experience by offering content that helps solve an issue the prospect may have and focus on optimizing conversion. Most people underestimate how difficult and resource intensive this is to do because it takes a ton of time involved with data gathering, analysis and creating the content. So after you are 80% happy with this (because that last 20% will take as long as that 80%), begin implementing your off-page strategies and work in conjunction with a continual effort on improving and adding on-page content. A core objective is focusing on great content and earning the links, so that is why I typically start there. As you know, this is a process that never ends. Good luck!