RLC - Understanding Phase Shifts
For 'intuition' of phase shifts in the RLC circuit above, notice that by KCL the current will have the same phase in all components in the loop. E.g.

$$
\theta_{I(t)}=\theta_{I_R(t)}=\theta_{I_L(t)}=\theta_{I_C(t)}
$$

Then remember that:


The phase of \$V_R\$ equals the phase of \$I_R\$.
The phase of \$V_C\$ lags the phase of \$I_C\$ by 90\$^\circ\$.
The phase of \$V_L\$ leads the phase of \$I_L\$ by 90\$^\circ\$.


$$\square$$

For the other question, none of the passive elements have gain > 1, but \$V_C\$ is the dominant term of the voltages at low frequency.