Hello Kevin, et al,
I will try and hit the highlights (let me know if I have missed anything.)
"Living in the round" is as much a cultural mindset as anything else...simply put, it's not easy and many that think they will like it, soon find they do not. So if you have lived in the round before great!...Proceed with a light, and happy heart...If not...really think about it. Most cultures that live in the round are living nomadic or semi nomadic lives, and/or living in very "big" round space with multiple floors and some flat surfaces. This is not a "right or wrong" concept...just an architecture choice that many choose without really comprehending what they are picking.
Oak, Osage,
locust and/or several others (until you get into something like Mesquite) all cut about the same if your tools are of good quality and properly sharpened...so there really is not a big difference in what they do to tools (especially power tools or really sharp good hand tools.) If Locust is a 10 in this group...oak is a 9.5 or better and Osage is in between. Also, timber frames are (for the most part) cut "wet" (or in the "green") and this has a huge effect in how they cut. Oiling, and/or "wetting" your edge and the wood also facilitates cutting and clearing the chips.
If you do choose to proceed "in the round" little exceeds a corbelled or reciprocal roof. I have CADs for both styles, and there are many other "mondala" variations (as you have seen and shared) that are stunning. They can be a little challenging to assemble, and if "truly jointed" much more difficult to layout and cut. I will warn you that just because you see so many DIYers doing these...does not mean they are doing them well or that they are designed and engineer properly. Your space seems small enough that you
should have little issue.
If you are working with "round material" (these are called "bolts") you are going to have much more of a challenge in layout and joinery unless you are going for the "really really rough look," in your joints and workmanship. In the size range you have mentioned, you very well may find plenty of Osage that will fulfill your needs...especially in Missouri. If this is your first "full scale project" I strongly recommend more than thorough (and longer than normal) planning, modelling and blue prints both in elevation and plan.
Let me know if I can be of further assistance.
Regards,
j