understanding react hook useEffect inner working

i started working on a project using react as frontend framework, been a good journey, a lot a of doc and ready to use plugins. but i'm still trying to understand the different between these two pieces of code

import {useQuery} from "react-query";
import {GET_CURRENT_USER_QUERY} from "../sections/shared/user/requests/user-requests";
import {useContext, useEffect} from "react";
import {ClientContext} from "../contexts/RequestGraphqlClientContext";

// ----------------------------------------------------------------------

export default function MyAvatar({...other}: AvatarProps) {
    const queryClient = useContext(ClientContext)
    const [user, setUser] = useState(null)

    if (!queryClient) {
        throw new Error(`missing a UseGraphQLProvider`)
    }

    const {data, isLoading, isSuccess} = useQuery('me', () => {
        return queryClient.request(GET_CURRENT_USER_QUERY)
    })

    useEffect(() => {
        if (data && isSuccess) {
            setUser(data.me)
        }
    }, [data, isSuccess])
    

and this one

import {useQuery} from "react-query";
import {GET_CURRENT_USER_QUERY} from "../sections/shared/user/requests/user-requests";
import {useContext, useEffect} from "react";
import {ClientContext} from "../contexts/RequestGraphqlClientContext";

// ----------------------------------------------------------------------

export default function MyAvatar({...other}: AvatarProps) {
    const queryClient = useContext(ClientContext)
    const [user, setUser] = useState(null)

    if (!queryClient) {
        throw new Error(`missing a UseGraphQLProvider`)
    }

    const {data, isLoading, isSuccess} = useQuery('me', () => {
        return queryClient.request(GET_CURRENT_USER_QUERY)
    })
    
    if(data && isSuccess) {
        setUser(data.me)
    }

what i know is that useEffect is used to watch variable content change and trigger the effect, like computed property in vuejs ( coming from vue ). so what will be the different between making the user mutation inside a useEffect or just inside the function body ( called each time for each render ?)