Pulse shaping with root-raised cosine filter for a non-Gaussian channel
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Correct.
The roll-off factor $\beta \in [0,1]$. If $R_p$ is the pulse (or symbol) rate, then the pulse bandwidth is $B=(1+\beta)R_p/2$. When $\beta=0$, the pulse is a sinc and the bandwidth is the smallest possible. For $\beta&gt;0$, the factor $1+\beta$ is the &quot;excess&quot; (not &quot;sacrificial&quot;) bandwidth.
The AWGN channel does not distort the input signal, only white Gaussian noise is added to it. The density of the noise is Gaussian (normal), not the channels' impulse response. The noise, being a signal, cannot be linear or non-linear (only systems have this property).
RRC and other Nyquist pulses can avoid ISI in many different channels. For example, in  a frequency selective channel, after linear equalization the received signal has no ISI. RRC pulses remain the most popular in practice, in all kinds of channels.