Not if you don't hear distortions, yes it is possible if you listen loud, hear distortions and you continue to listen at high level with very audible distortions, though it may take a long time before it gets damaged depending on many factors.
You can use just about any speakers with any amplifier, it all depends on how you use it. In your case, the speakers sensitivity specs claimed 98 dB but James measured value was 92.1 dB/2.83 V/m so 8 W will get you about 90 dB at 10 ft.
If you don't listen louder than say 70 dB average and sit within 10-12 feet, using 4 or 8 ohm taps won't make much difference. People will tell you to try both and use the one that sounds better, many will tell you they heard big differences, but they could say whatever they think they heard and/or say anything they want without any need to prove anything. To me, it is best to stick with manufacturer's recommendations.
I would think that based on the impedance curve, it is better to use one amp to drive the woofers using the 4 ohm tap and the other amp to drive the tweeters using the 8 ohm tap. That's based on the measurements in James review, in practice, I doubt you can hear any difference in a blind test, unless you push the amp to point you could hear distortions.
With those big speakers, you will be far better driving with higher output amps, even two $90 monoblock Fosi class D chip amps will sound better, with far lower distortions and noise and those tube amps you have now, unless you are one of those who enjoy the sound of distortion of such tube amps.
