Sudden drop in executive function from 90% to 25% (age matched) over six months period while memory and processing speed remain 90+%, along with episodes of semantic paraphasia, olfactory hallucination, and transient altered mental status/confusion?

These symptoms are beyond simple cognitive screening and warrant going directly for cognitive loss function administered best by a mental health professional. However, it's mandatory that you also be evaluated to rule out depression, certain medications ,deficiency states &,toxicity as causes of your symptoms. A complete medical & neurological checkup with pertinent testing should be done as well

Strongly urge scheduling a visit with a behavioral neurologist for a full dementia evaluation. But, in addition, your post raises concerns to me regarding potential complex partial seizures, and an EEG can potentially clarify. Would urge, at this point, avoiding driving, activities at heights, use of power equipment, taking bath or swimming alone.