Resting oxygen saturation is 98-100 consistently. During intense exercise (85% mhr), it drops to 93-94. Is this normal?

It is fine. As long as it does not drop below 90% it is ok. You do not say what your health problems are or if you were a smoker. But it sounds like you are ok.
O2 Saturation. The above numbers are fine for your o2 saturation rate. And, yes, it should go up with exercise.