You wont have any issues with your water quality when it comes to shrimp and snails pooping and creating ammonia, your cycled tank will turn it all into algae food and help that grow! Which in turn will be eaten by the shrimps
The only thing that will swing the balance is feeding too much food into the tank putting the cycle under too much pressure. This will either make toxic ammonia and nitrites hang around until its processed into nitrates or it will get turned directly into nitrates but the quantity that is produced will be too much for the algae to process and use as a food source quickly for its self making it hang around in the water, ideally you don't want any ammonia, nitrites or nitrates lingering in the water.
If you do get this issue you will see the shrimps being very un happy and some *may* die if the issue is Ammonia or Nitrites or HIGH levels of nitrates, but if you do a water change to dilute the toxic levels it will help keep the tank healthy, or you can just dump a vial of biodigest (bottled bacteria) in and it will almost instantly turn the ammonia, nitrites and nitrates into food the algae or macroalgae can use for around 2 weeks.