Signal integrity in active filter
For practical cheap amplifiers, with limited bandwidth, their output impedance begins to rise with frequency. If you've chosen a reasonable amplifier, this will be well into the stopband. At a frequency where the output impedance becomes significant, it fails to control the feedthrough of signal through R1 and C1 directly to the output. This results in a stopband lift, above the expected 40dB/decade fall. Smaller capacitors mitigate this effect.

Keep your Cs well above 100pF or so, to avoid inaccuracy due to strays.

The amplifier input bias current is provided through R. The DC offset across the stage will increase as 2R times the amplifier input bias current. However, for most practical cheap amplifiers, this will be dwarfed by the input offset voltage.