The specific performance is that everything is normal, but there are slight vomiting or diarrhea symptoms.
The diet of gastrointestinal sensitive cats needs to pay attention to two points: quantitative and single.
You say cats will vomit if they eat too much, so give that much at a time, not too much. But the frequency of feeding can be increased once or twice a day. Don't put a lot of dry food at once, because cats will continue to eat without feeling full, and then cause vomiting.
In addition to cat food, snacks should be given less or even not. Especially snacks with high oil content.
You can choose cat food specially prepared for cats with sensitive stomachs. Such as Royal, Sears and other brands, all have this one.
In addition, the cat can be fed lactase to regulate the stomach. It's very cheap, and it's also sold in pharmacies. Just take two tablets twice a day.