1. Some cats are talkers. MC's are often very chirpy, conversational talkers. Mine will even talk to herself. IME, the more you respond to the meows, the more meows you'll get (it's the process of "training the humans"). I love talkative cats, and Assumpta and I will meow back and forth at each other quite a bit, or she'll meow and I'll talk and she'll meow. Start to worry if the meowing becomes unusual, changes drastically in sound or frequency, or seems to be precipitated by touching a particular body part.
2. Excessive grooming can be a problem if he is licking himself bald or pulling his fur out. In longhaired cats, lots of grooming can cause hairballs, so daily brushing will help pull the dead fur out...the more you brush out, the less he'll swallow. Also, dry or itchy skin can cause excessive grooming activity, especially in the winter when the air is dry, so making sure that he gets enough fat in his diet can help with dry skin and dandruff.
3. Some cats do better with fresh (not dried) catnip. If he's having problems tolerating it, try growing some over the summer and see if he has the same reaction to the fresh stuff, which will be less powerful.
4. Male cats don't have "cycles," but their female owners may. My cat treats me very differently depending on what time of month it is. It doesn't have anything to do with her, she's just reacting to my changing physical state.