As far as I’m aware, the yeasts in kefir do compete with candida (and other yeasts). They’re also transient, so they won’t be able to colonise your gut.
As for tolerating it, it’s hard to say. At first, it gave me headaches and when I ate the grains I felt like I did after an 80bn probiotic capsule. Now it doesn’t really bother me at all. I’ve eaten 3/4 cup of grains in a day with a litre of kefir. Just start small and judge your reactions.