Explanation:

Box 1: Append Queries as New.
There are two primary ways of combining queries: merging and appending.
* When you have one or more columns that you'd like to add to another query, you merge the queries.
* When you have additional rows of data that you'd like to add to an existing query, you append the query.
Box 2: Disable loading the query to the data model
For every query that loads into model memory will be consumed. and Memory is our asset in the Model, less memory consumption leads to better performance in most of the cases. The best approach is to disable loading.
Reference:
https://docs.microsoft.com/en-us/power-query/append-queries
https://community.powerbi.com/t5/Power-Query/Append-vs-Append-as-new-for-performance/td-p/1822710