Some BJT based OPs need a low source impedance to get a very low noise level or more accurate there best noise figure. However this does not mean that the amplifier is loading the source with this impedance. The input impedance of the amplifier circuit can be higher.
Ideally the resistor to ground after the input capacitor is larger by something like a factor of 10 than needed to get the low frequency limit at 0.1 Hz. This reduces the loading to the source and also avoids much of the resistor noise in the transition region. The exact low frequency cut of that has to be set in a later stage, behind the initial amplification. This could also be in the digital domain, if the signal goes to an ADC anyway.
Still it is problematic to have OPs that need a low impedance source, as it needs a huge capacitor, that can represent there own problems.
Using Spice models to compare OP performance is a little tricky - not all models are really accurate when it comes to details like current noise.
Usually the data-sheets are still a little more reliable. From the DS performance the OPA27 is not that good.
Testing low noise in real life is not that bad. There is another parallel thread on such tests on AZ OPs. It's mainly setting up an amplifier for 2 input resistors (one near zero and one suitable for the OP, so that current noise dominates). The behavior with a different source impedance can than be calculated to a good approximation. Only AZ OP may need extra test with small capacity to ground, as there can be effects from short input current spikes, that makes them possibly less predictable. The noise test can be done with DC coupling, so no need to wait for a coupling cap to settle at the input.
To get noise data down to 0.1 Hz one might want to take something like 10 times the minium 10 second interval to average over some random parts like popcorn noise. Still this would be something like a few minutes to measure and maybe 30 minutes for thermal settling. Just looking directly for peak to peak noise is not very effective. The better way today is more like an FFT to get the noise spectrum.