First of all, ceramics are used when machining Ni and Co based alloys (not Titanium alloys because does exist the risk of fire) and mostly for roughing then finishing, because the undesired effect on surface machined. For roughing, the best solution is to have an entering angle of 45 degrees or even smaller.
Ceramics with negative geometries can generate cutting forces much higher than carbide inserts which could not be used on thin walled components.
Because of their tendency to notch wear, round inserts are used in low entry angle. For larger depth of cut, square inserts, with the entering angle of 45 degrees, are used for best productivity. The main problem for this kind of inserts is shape of components which not allow its' use for a lot of operations.