Non-inverting Buffer, Increase Rf for more gain. Add a power transistor to Vout for power.
Yes, you have it right. That is how it's done. Switch inputs for inverting. You can always go back and mess with gain.
The signal buffer complete we measure output then transition to a conversation about power at the second stage.

Let's review NPN TIP120 is a medium power Darlington, it is important at this point to remind you of safety. We are talking power now.
We ask how many amps and volts do you need? Then we can set up the power transistor. Power does real work, it is not a small signal.
Look at figure 6 link below, notice active region, Does 4V and 4A work for you or do you want to operate at different active region ?
That is why we ask, we don't like to remain in small signal purgatory but the question is always too hard for a simple answer.
No. that's not any good I need 30V and 2A, I am not using a low voltage Arduino, ok lets find a medium power transistor for this analog driver.
TIP120 - Plastic Medium-Power Complementary Silicon Transistors (onsemi.com)

 

By my RLC band stop filter is not 50 Ohms?

nope... in fact by definition filter impedance is changing in accordance with frequency. without change, circuit would have same effect on any frequency and then it would not be able to suppress certain frequencies. this change can be measured or calculated (and plotted).

you have series RLC... if this was just LC then theoretical impedance at resonance would be 0 Ohm (and it cannot be negative). hence at any other frequency, impedance would be more than that. at low frequencies C would be the stopping power... at higher frequencies that would be L. and the point with lowest impedance is the resonance point. for 100uF and 100nH that works out to some 50Hz and this is inside your mentioned range 5-640 Hz... but you have R in series with LC and this adds 300 Ohm to the whatever impedance of LC circuit is. so the lowest impedance of complete RLC (at the resonance) is going to be the value of R.

since you plan to use signal generator that outputs 2V, your filter will never see current greater than 2V / 300 Ohm=6.7mA
and since your generator output is good for 20mA, you are all set. there is no need for 741.