5V PWM 0-100% duty cycle output should generate 0-100mV
If you are going to use an op-amp you might as well implement a unity gain sallen key 2nd order low pass filter: -



This will overcome the problem of the first low pass fitler being hampered by the input impedance of the 2nd low pass filter.

You can use this calculator from Okawa Electronic Design to plug in values but I would go for two 1k resistors with C1 at 10uF and C2 a bit smaller, maybe 2.2 uF.

You don't say in your question what the PWM amplitude is but, adding a resistor from the junction of R1 and R2 to ground can produce the required attenuation but the parallel combination of R1 and that extra resistor is the value of R1 to be used in the calculator.

In your 2nd schematic I have no idea why you are attaching the op-amp power to the input voltage waveform. Recipe for rubbish is my thinking. It may look like it's working in a sim but it won't work in practise because, in practise, you need nominally a 10 nF or 100 nF op-amp power-rail decoupler to avoid op-amp mis-workings.