Hi rockalicious,
From a quality perspective … the Dolcezza and all the Greensleep mattresses use all high quality materials.
The S300 dowel foundation would be similar to a tension adjustable slatted system where the tension or firmness of different areas of the foundation can be adjusted to fine tune the sleeping system in terms of support and firmness under different areas of the body.
Post #2 here and the posts it links to have more information and my thoughts about the Dolcezza and the dowel foundation and may be helpful along with a forum search on Dolcezza or on Greensleep.
I don’t think I would have warned against purchasing the dowels outright because it would depend on how someone tested it. My only caution as you mentioned would be to be aware that if you test it one way (with or without the dowels) and then purchase something different that it wouldn’t be the same as what you tested. If someone intended to purchase it without the dowel foundation then I would make sure that they test it that way in the mattress configuration and layer choices that is the best “fit” by itself to make sure it is suitable in terms of PPP without the S300.
Phoenix