Q value of a passive single stage RC low pass filter
First, \$\alpha = 2 \zeta\$, \$\alpha\$ (damping constant) is used in filters, and typically \$\zeta\$ is used in controls. 

Q is defined as \$ Q = \dfrac {f_o}{\Delta f}\ (= \dfrac{1}{\alpha}) \$. It is a band pass parameter and does not apply to first order filters. 

If you want to change the step response, you're going to have to change the damping. In the case of the Sallen-Key, that involves changing the gain of the amplifier. This is where you have to start being careful. Damping is set based off the approximation you chose. As an example, for a Butterworth approximation \$\alpha = 1.414\$. If you want a faster rise time, you'll want a lower damping constant. Look at the Chebyshev =approximations. You do need to be aware that there will be overshoot with those approximations.

Cascading filters does not have the effect you think it does. For example, simply cascading two second order Butterworth low pass filters for example, does not equal a fourth order Butterworth low pass. There are tables of common approximations and the appropriate correction factors that need to be considered when cascading filters.