One of purrelys biggest weaknesses is finding stuff to do with left over monsters on their board or alternative paths if purrely or purrelyly get negated. The yummy cards resolves a lot of those issues by just allowing you to convert spent monsters into a yummy combo. This can also work to help bait out negates allowing your purrelys to stick. This is made especially powerful given a hornet drones gets you everything you need from a single card. The other alternative to this is of course including a fiendsmith package, however that would sully the adorableness of these wittle guys
The deck also has a lot that can be changed with the extra. You could for example cut a copy of snatchy for ty-phon, a copy of noir or plump for herald, or ditch the striker package for songs of the dominators main, and a copy of S:P in the extra if you so wish. While I personally prefer this distribution with my own play style focussing more on the purrelys it's still a work in progress and the environment of your locals may differ.