KLK If they are two inches Below the mulch and you have at least a couple inches of mulch you should be just fine: i.e. tuber is 4 inches below somekind of garden soil/mulch.
That describes many of mine and they are coming up just fine and have fared well in the past planted this way.

I usually end up top dressing each plant with more compost material as the season wears on anyway, so that gives more protection and moisture retention.

Full sun is perfect. 90 days to bloom time, but often earlier by 10-20 days- depends on variety, weather etc.

Fertilizer is your choice. I have used Osmocote flower and veggie extended release for years, but this year I'm going with 10-10-10 to see if I get more blooms. It lasts for 60 days. I am too busy to use a fertilizer more often.

Sounds like you're off to a good start this year.