I will do my best to provide some information that will help you with the above questions.
1. Are you asking for information on dashboards being summarized vs. transactional?
2. Geocoding data can be used to creates Vizzes in Tableau, more information can be found here: Plotting Geographic Data Using Custom Longitude and Latitude Values | Tableau Software
3. This question can be a little tricky to answer and depends on your environment or culture at your company. Tableau is designed to be simple enough to use and powerful enough to create the data visualizations of th future.
4. For information about the correlation use in Tableau, I would check the following document on the Tableau Community; Covariance, Trend Lines, Correlation Coefficient R and R-Squared
5. For performance in regards to the filters in Tableau, it is important ot understand the order of operations that Tableau uses when rendering the Viz: Tableau's Order of Operations
NOTE: There are suggestions in our performance documentation about the use of filters to hep with performance, whether it be through reduction of data in the view overall, or by adding filters to context.
6. The "Out of Memory" error is encountered when the program does not have enough memory to process the query. More information can be found here: Out of Memory Error When Blending Few Million Rows | Tableau Software
Try reducing the number of rows prior to any joins or blends.
Hope this helps!