No, 192 kbps is not the best sounding constant bit rate (CBR) coding...(BTW, "codec" is actually short for encoder/decoder.)
The higher the bitrate, the better sounding mp3 you will generate. I think you may be able to go up to 420 kbps CBR with LAME. The problem is that the higher the bit rate, the less compression of the file you achieve. I found, for my use (iPod while traveling), that the size of the mp3s generated at 192 kbps CBR was about right. After learning more about coding mp3s, I shifted to the -alt preset extreme, which codes at a variable bit rate. The theory is that different temporal chunks of the music are encoded at different sample rates based on the complexity of the chunk being converted. As a result, there will be parts encoded at a rate higher than 192 kbps, and parts encoded at less than 192 kbps. But, I've found that the overall size of the resulting mp3 is about the same size as the mp3s I created at 192 kbps CBR, they just sound better to me.
I believe the -alt presets were created by the coding community as being the optimal sound you can achieve for a particular compression ratio. There are other -alt presets (I use "extreme") that are their best shot at optimal sound for other compression ratios. Its all about how much compromise you are willing to live with for the sake of disk space used.