The lift capacity of your BCD determines how much weight the BCD can support while remaining buoyant. Choose one that can handle the weight of your gear and the conditions of your usual dive spots. This lift capacity is determined by the size and volume of the bladders and can usually not be changed after the purchase.
How much lift you need depends on several factors like your own body weight, the type of exposure suit, what kind of extra equipment you carry, the water type, and the number of tanks you take on your dive.
If you are a recreational diver, you don’t need to worry about this unless you dive different setups (double tanks, stage bottles, super heavy camera equipment etc.)
The heavier your specific weight (so the sum of all the components above) the more lift capacity is required.
In general, single-sized BCDs by design offer enough lift capacity for recreational diving when bought in the right size. As such, the amount rises when you buy an M or L instead of XS or S. In most cases, you will not need to worry about the lift if you only dive recreationally and without heavy equipment like double tanks or professional video equipment.
The only time you could ever have too little or too much would be if you use a BCD that’s several (read: more than 3) sizes too small or big while carrying excessive extra weight or none at all.
30-40 lbs of lift are sufficient for 90%+ of all divers.
Even when buying a wing bladder for your backplate setup, most divers tend to greatly overestimate the required amount of lift they require. Most divers will be completely happy and safe with a bladder in the range of 30-40 lbs no matter their size or diving requirements.