I'm no tube expert or guru, but I'm trying to learn on my own. So take my comments from that point of view. At any rate, I stuck you circuits into a simulator, using different tubes and passives than your example. It would appear that Circuit B has WAY more even-order distortion than Circuit A. Circuit A appears to be a very clean method.
Now, to your questions,:
Why Circuit A sounds darker than Circuit B?
Without the extra harmonics of Circuit B, Circuit A will sound darker.
Which circuit will give more "triode" sound?
If "triode" sound to you means more even-order distortion, than Circuit B is the ticket.
Are my designs wrong?
Define "wrong."
What could be improved?
Is improvement necessary?