Performance Analyzer separates the work behind a visual into a DAX query, visual display and other time. Start recording, refresh the visuals, then inspect the slowest entries. A long total is a starting point for investigation; changing a title can't repair a costly query.
This simulator reports deterministic estimates based on its model and visuals. It isn't measuring Power BI Desktop or the speed of your computer. The estimates respond to row count, cardinality, relationships and calculation shape, which lets you compare a change under the same conditions. Record a baseline, change one thing, and refresh again. A smaller result after hiding useful fields isn't an improvement if the report no longer answers the question. Use model size details to explain why a change reduces work.