What does this have to do with anything? Audio in AE is a crutch, a utility, an auxiliary thing. Of course you can obsess about the minutia of audio sample rates and bith depth all day, but it won't do anything. If at all it's only relevant for the realtime playback because naturally you will want to avoid lag and buffer delays due to realtime resampling. Everything beyond that is utterly moot.
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video standard for production is 48 kHz 16-bit minimum. 44.1 is a consumer standard and should not be used for anything other than consumer delivery.
Unless you have specific delivery specifications you should not see the word Custom in your composition settings or your render settings. Let AE manage the audio.
If it were me I would either ask for a 48 kHz master that was 16bit or better and do any audio manipulation needed with that, or I would do the audio manipulation in Audition using its native 32-bit audio processing and render a 48 kHz 16 or 14 bit master to use for rendering.
AE will handle almost any audio in the timeline but sometimes you will run into rendering or mixing problems if you use Mp3 or other highly compressed audio. OTT, as Muylenium said, you are making a big fuss about something that does not matter. What does matter is that you do not customize your comp or render settings unless you have studied enough to be confident in your decision to mess with the standards and you are willing to suffer the consequences of ren rendering a product that will not playback or perform as expected.