Some better examples of 16x media can be safely burned at 12x or 16x, it really depends on how well it fits the firmware of your particular drive. We recommend Verbatim AZO 16x disks (not the Verbatim Life Series) and we also recommend Taiyo Yuden 16x and 8x media. Both are readily available online.
I tend to burn at 8x too, though I've found that burning MCC-004 (Verbatim 16x +R), I can increase that to 12x with no issues whatsoever in my drives.
I prefer Taiyo Yuden 8x +R, but burn it at 8x. Many people in the past would "overspeed" it to 12 or 16x, but there isn't any compelling reason to do so in my opinion.
Nominal burning speed does not affect or inhibit reading speed. That is normally a function of the drive and its capabilities. If you have a bad burn, with a lot of writing errors stacked up, then yes, it can slow down the read.