It depends on your rate of consumption. Kalk is usually used in top off water. If you can maintain your levels by using kalk in your top off water, that's all you need. The thing with kalk is you can only make it a certain strength (2 tbsp/gal max, but it can be weaker), so if you have a somewhat low demand you may be OK. I used kalk (Mrs Wages) in the past, but it alone couldn't keep up with the demand.
Calcium supplements won't affect pH. Depending on exactly which alk supplement you use, it may or may not affect pH.