Tums is calcium carbonate, not sodium bicarbonate.
The bicarb is what really matters
So is Tums safe since it isn't bicarbonate? I take it every day to counteract acidic foods.
The excess calcium can greatly increase your risk of kidney stones.
This is myth, Ca actually can reduce kidney stones while Na increases the probability they will develop. Ca could have negative cardiac effects above 1200mg per day though.
CaCO3 and NaHCO3 effect pH in similar ways, Calcium Carbonate is the stronger alkaline buffer though because it can pick up 2 H+ where as bicarb alread has an H+. Both can form bicarbonate ions depending on the pH.