Mrs ixv has one low-risk, non-life-threatening, pre-existing condition and I have two. I have used the BankWest MC travel insurance, the only credit card insurance I could find which covers pre-existing conditions. It was with Zurich. They had a simple on-line assessment tool and they covered our conditions for an "administrative fee" of $45 pp per trip. Last year BankWest changed to Allianz. Assessment is by phone. They covered us for $75 pp per trip.
Our trips this year are on various combinations of award and revenue tickets. I checked whether this would be covered, but no, to qualify for BankWest insurance, one needs to have a "return ticket" for each trip. So I had to look for other insurance. I selected QBE's annual policy. I had to complete an on-line form. Writing in of details was required, a lot more time-consuming than the Zurich form. The form was then assessed by their medical staff and the next day I received their answer: no extra charges, Mrs. jxv's condition accepted, one of my conditions accepted with a $75000 liability limit, the other not covered at all. Because of the low risk I decided to accept.
I hope my experiences are useful to you!