You can opt OUT of Select and still choose the 70% royalty option. Granted some county sales will be at 35%.
Any sales on smashwords in addition to Amazon is a good thing...be it one sale or a billion.
IMO Select is only useful if you need the free promo days to get your book out there (esp 1st in a series). My debut novel is in Select at the moment and I am counting down the days until I break it out of jail! I have it on Smashwords and Lulu.com (but not available to the public) and am just ithching to make them active again. The 2nd book has been out for two days and I did NOT add it to Select. I am DONE with giving any copies away. So done with it.
I long ago opted out of Smashwords for a variety of reasons, the main one being that I wasn't happy with their formatting. It's just not professional, IMHO. I am currently running an experiment there, because SW has recently announced support for the epub format, meaning that one can control how the book looks and doesn't have to go through the infamous Meatgrinder. That's presently on hold because Apple requires that the author's name be on the cover, and in this case mine wasn't. I'll get back to that in a while.
But for the most part I prefer to upload directly. Your two main retailers are Apple and Barnes & Noble, plus there's a Canadian outfit called Kobo. You can upload to Apple through Lulu.com which will create an epub from a Word document. You can upload to B&N and Kobo directly, again using a Word doc if that's your choice. You get paid more quickly by going direct, and in most cases you get a larger share of the retail price.
Kindle Select does offer some advantages, the main one being the ability to "loan" your book to Amazon Prime subscribers for a fee, but Select has been so abused in the past year that now it is mostly a destructive force, for authors and for Amazon, to the point where the company now appears to be trying to rein it in. I think you're much better off having the freedom to publish elsewhere. What you lose by not being in Select will be more than made up by your sales at B&N, Apple, and Kobo.
Just be careful with lulu.com and read the small print very carefully. I didn't and wasn't best pleased when I discovered that, despite the big print saying I was getting a royalty of £3 something per book, that only means sales from the lulu site. Most of my paperback sales were through Amazon and between them they take a huge percentage of your royalty. I think I actually only get 11p now per book. Lesson learned!!
While I'm sure some people like Smashwords, it's never garnered a lot of sales for me, while the Kindle has. I also found its process to be annoying, as I would often have to put it through multiple submissions before finally finding the right mix for a novel to be accepted, The "changes" they required were never in my favor, so I just stopped submitting my novels to them.
Thanks all for the input. This was very helpful! I have just uploaded a book to SW this week. I will see what happens. And yes, I did struggle with the formatting a bit with the Meatgrinder. I will give it a little time and then experiment in going directly as recommended. Thanks so much!