Where did you hear that about RICOH CD-R ? I have not seen any RICOH CD-R in the USA recently at all. I highly doubt that you would get any in an Imation package and I highly doubt that you could find any type of made in Japan RICOH media, since Ritek Taiwan produces media for RICOH nowadays.
The Imation CD-R that I have is made by CMC, and works just fine.
@second question: As you've discovered firsthand, some discs just burn better at higher speeds depending on the dye and/or write strategy of the burner.
Moser Baer CD-R is actually pretty good from my own experience.
I have some Office Depot brand Moser Baer CD-R, which burns well in a range of writers.