If you feel emds are good, then use them. In all the 100's of sites I work directly and indirectly on, I can't recall a single emd that does well, and because of that, I will never use them or advise my clients or others to use them. My responses with you are based on experience, not guess work or what I've read. I write when I feel inspired or I spot some pattern or something useful based on sites I work on and by analysing competitors of those sites.
Ever since the emd update in sep 2020 emds stopped working well. pmds are still ok, but even at that I wouldn't use more than 1 topical keyword in a domain. "toasterworld.com" etc, never "toasterreviewworld.com".
If you've had actual positive experiences with emds then I would enjoy hearing your feedback about how it went for you.
1 link, but that link will appear on on the homepage, the article page, sometimes a tag page, and usually the category page. Also sometimes author pages or archive pages. I vary it on my networks, but I usually like it to appear in a few places. 90% of the juice comes from the homepage, but it's a few extra links, and it means that a high % of your links aren't just from the homepage. If every pbn link gives you 3-6 links, then your homepage % is going to be < 10% if you have only a few other non-pbn links.
More is better. I recommend 700+ words, but feel free to go for 1000-1500 for a private pbn a p^2bn
For a private one I would do bigger articles, 1500 words, and link out to 4-5 sites. You don't really lose any power. Link juice doesn't really work like that, where if you link to 10 sites, you only get 10% of the juice, otherwise your best option would be a 300 word article with 1 link and nothing else.
The only reason you want public pbns to have lower obl is for the safety. Of course, when you're talking about having 30-40 posts on the homepage, with 2 links each, it will definitely reduce the power.
The absolute best way, and the way that will look very natural is to have 1 big 3000 word article and link to about 10-12 different sites. 2-4 can be yours, and the rest just general related authority sites. That only works if you have sites in the similar niches where that big article will be good for them all. (Note, that you don't want an article "Toaster Guide", to link to your toaster review page. You want something more natural like "The 7 Most Delicious Breakfasts In the World", so that could link to any site related to food, kitchen or even potentially travel if you modify it to a guide to breakfasts from around the world.
The more cost effective way to build your pbn is to use it for 5-6 of your sites, but be wary of footprints. You can't build 100 pbns, with 6x500 word articles, each linking to one of your money sites. You would vary, having site a, b, c on some, site b, d on others, a, e, f on others, a, b, c, d, e and f on some, and including other articles linking to other sites. This is of course higher risk, but 1 pbn for 6 money sites is quite a saving.
But, if you only build a super strong pbn with 10 say, $500-$1000 domains, you can quite happily just link to all your sites from every pbn site, but you'd mix in links to other sites too. Just don't do this with 30, 40, 50+ because it's too much of a footprint.
My pbn content is done by my own team of writers that I've trained in how to use anchors in content properly. That's the most important thing.
Number of RDs is easy to manipulate. You could buy a couple packages on fiverr which will inrease it by 1000+ for $10-$15 total.
In my opinion, RDs isn't even something google measures. Why would they? It's too simplistic a metric.
They have an algorithm which passes trust and link juice from pages to other pages. It's operating on a page by page basis. They don't really think about "sites" either. They don't class a site as being in a particular niche. It just wouldn't be practical. This is what google operate with and what makes them tick :-
1) Pages. Passing juice from pages to pages.
2) Semantics. Understanding context, how pages relate, and what a page is about.
3) Trust/authority which is one of the things that is site wide.
They look at all the pages on your site. From this, they don't classify your "site". They classify you under various topics. Here's an example.
Let's say we have a site with 20 pages
8 on cats
6 general, 2 cat behavior
12 on dogs, all dog training
Now, they have a giant database of topics. They understand how these topics relate to each other, and they're connected with weights. It's a big interconnected network.
As humans we have one. If I say cats, what do you think of? Animals? Tigers? Water? Scratching? Lots of things. Maybe scratching is a 6/10 relation. tigers is a 7/10, water is a 3 and so on. We also understand, and so does google, that cats are not tigers, and tigers are a type of big cat, so a site about cats is not going to rank for tigers, but that it's a related topic.
Now, based on your pages, google builds a kind of topical matrix about your site. HOW they do this is a mystery. It'll include factors like, how many pages are about the topic, how many pages are about similar topics, internal links, length of content, where you link to, and who links to you.
But they certainly do not classify a site as being in any niche. It's WAY too simplistic and error-prone. There are no "niches". There are matrices of topics, with weights, that are used in determining how you'll rank for keywords.
From the above you'd get some sort of matrix, that would say your site has good authority for dog training, and any dog training keywords will have a stronger weighting factor weighed against them. So you may end up position #14 for a new dog training keyword, instead of say 56 if you had zero dog training content, and 100+ if you had NO animal content at all.
So google are quite simply operating with pages. Page to page. Passing juice and building this topical matix of your site. Trust, will be site-wide, and may also be influenced by the topical matrix. Ie, you might have high trust in dogs/cats, and low trust in health. This is purely a guess, but it makes sense and it's how I would do it. I trust my plumber to plumb, not to do brain surgery, and I don't trust my brain surgeon to fix my pipes.
Appreciate your thoughts though. The back and forth creates interesting discussions and exchanges.