Two downsides of using Vue.js are performance in first page load and SEO. In order to solve or improve those, there are two things I always do: pre-render all pages I can and use vue-meta to include the correspondent meta-tags.
Vuexfire is great to bind a Firestore query to your state and keep it in sync but the moment you try to add the Firestore pagination methods like startAfter to your query, things start to fall apart. I explain you how to create a load more pagination using Vuexfire and a few custom mutations.
One of the most common problems to solve when building a Vue.js project is state management. While Vuex is great, you always end up writting a ton of actions, mutations and getters. If your application backend is Firebase, Vuexfire can save you a lot of time and quite a few lines of code.