Catalanc: I think that maybe you are asking the wrong question, or at least focused maybe too much on "the number". I don't know if anyone can tell you whether it's 20-degrees, 22, 25, whatever - there are too many other variables like waves and chop and comfort of your crew.
I've been sailing about 5-years. We were knocked down by a gust on the "sea trial" - our very first time out - before we even bought the boat, terrifying our 2-young daughters, soaking my wife and the captain/broker, and enabling us to test the scuppers as they slowly drained water from the cockpit. I bought the boat anyway, and I've never experienced a similar problem. But, for years, my wife and kids would watch the gauge and start complaining whenever we approached 10-degrees, and howl loudly if we heeled more than 10-degrees.
We bought our 2nd, newer model, C22 about a year ago. The first thing I did was to remove the gauge that the PO had installed. That changed everything. No more focus on "the number". The discussions are now much less frequent and more about control and their comfort. I sail conservatively with my family, and reserve my adrenaline rush for Saturday racing in our C22 fleet with a buddy. I also give my wife and kids the jib sheets - they get to decide when the heel is too much for their comfort and can ease the sheet to spill air.
My suggestion - focus on control and comfort. Like you, I mostly sail on an inland lake that can be gusty. Watch your overall conditions and especially the wind, how it hits other boats, how it affects flags and trees, and how it effects the water surface (polarized sun glasses really help to see the wind disturbances on the water surface). I personally think less than about 20-degrees is best, I ease the sheets in a heavy gust (when in doubt, let 'em out), and I watch the conditions constantly. 30-degrees heel in a steady wind may be just fine, but in variable wind, the next gust or increase in wind speed may mean trouble.
Welcome to C22 sailing - always great when we get a convert from the motoring side of boating. Enjoy the new freedoms and challenges of sailing.
- Bob