The word Sefirah is not related to the Greek word sphere although as early as the Bahir it is related to the Hebrew word sappirot, or sapphires.
Gershom Scholem, Kabbalah
I've been ''campaigning'' against spheres for some time now and once again the topic has resurfaced* along with a lot of the other baggage of the 'Hermetic Qabalah'. I am not saying that spheres are entirely useless but they do stand in the way of a lot of other useful concepts that are at least as worthy, if not more, of your time. In Brickwork of Sapphire I explored the link between the word for Sefirot and Sapphires illustrating how this brickwork could be referring to the Tree of Life itself which resolves into a series of rhombuses/diamonds once you remove the spheres, which are only there in the first place to serve as text boxes. Removing those text boxes you are left with the Sefirot as vertices, or points where the lines meet on the cut stone or crystal. This idea and the accompanying language of quarrying, engraving and carving stone(s) permeates the Sefer Yetzirah the key source text in the development of the QBL as a whole.
Look at nature - bubbles are spheres, sure, but Earth isn't, its a misshapen blob. Cells aren't spheres in tissues like some perfect bubble wrap either they come in all kinds of blob shapes. Speaking of cells bearing in mind the idea of vertices when overlaying the Tree of Life on your body you are much more likely to benefit if you focus on your nervous system and the connections between the main nerves, and those connections are the ganglion which are hardly ''spheres''.
From a mathematical perspective, as we move up through dimensions, we have circles, spheres and then glomes or higher dimensional spheres to play with - if you are working with spheres you are intrinsically working in 3d excluding the dimensions of time and perspective from your work. When it comes to the Sefirot themselves you might find more traction in toroids and vortices - if not, try blobs.
*Re-surfaced is probably inaccurate, its always on the surface like so much ocean plastic, it just happened to drift into my field of vision again.