For what I know, the difference in DSD filters (which are all analogue) are just how far you will set the low pass filter. Due to the 1 bit nature of DSD, you can't apply any digital processing onto it and therefore analogue filter must be used to cut sampling noise out. The filters selection is just a choice for you to set where to cut off. AFAIK, there never seems to be a common standard on this setting so iFi just let you decide for yourself.
PCM filter is however a different matter. Standard filter and Minimum Phase are both common filter you will find on PCM based DAC. Standard gives linear measurement result on frequency response, but often less than ideal on phase and ringing. Minimum Phase doesn't have phase and ringing issue, but tends to roll-off at the upper treble. The audible difference is that often people will find Standard filter a bit sharper and more detailed on the top, but also grainy at time. Sometime people described it as 'digital sounding'. Opposite to Standard filter, Minimum Phase filter can be found on many higher end DAC because it tends to sound smoother and more musical, or 'analog sounding', if you will. Bit-Perfect is basically NOS, or Non-OverSampling. It is not exactly a filter per se but more on how the DAC chip is set to sample the signal. It is kind of complicated to fully explain it but the short version is that the DAC chip won't do extra processing to the signal and no filter is used on the output. Instead, it relies on human natural limitation of hearing to stop us from hearing any sampling noise. Because of how it works, it tends to be quite noisy and lousy on the measurement, but also being described as being the most analog, musical and life-like when compared to the common oversampling DAC (such as when you used the Standard and Minimum Phase filter). When it comes to choice, Standard and Minimum Phase filter have their own pros and cons so there isn't a technically better filter to use (though some manufacturer will argue they have developed better filter than the above two, but that's another story). As with Bit-Perfect filter, it is somewhat of a 'doing the wrong thing but has the right result' deal. Even supporter often can't fully explain why they prefer NOS.
The whole point, however, is that these filters are there for you to choose from. Despite all the theory, you get to decide which one you like better.
Onca again, that is as clear and helpful an expllanation as I've seen on the digital filter options. Thanks for putting ity in terms I can understand, ClieOS!