If your after faint things, you need the exposure length, generally the longer the exposure the higher SNR for the same total integration time, (within the limits of what your gear is capable of)
For sky brightness (I am in an orange sky zone) you can play with ISO to move the dynamic range however even on 30s exposures, at 800 iso my sky background is only about 3%, so easy to clean out.
Without tracking, use this tool,
https://www.lonelyspeck.com/advanced...me-calculator/ It actually corrects for how high in the sky your target is, however the higher your focal length, the shorter the exposure you can get away with, for tools like depp sky staker, you need to aim for 3 pixels or less, or it will fail detecting them because your stars are not round enough (also found out the hard way)