Guidance on how to assess the impact of multiple parallel SELECT queries

Setup: SQL Server 2019 on Azure VM. We have an application that, on a specific date, will execute multiple queries to load data into their system. These queries will be run via Databricks using an ODBC connection, and they will primarily consist of SELECT statements with various joins and filters. I'm looking for guidance on how to assess whether the workload generated by these queries could be problematic. Specifically, I want to understand what metrics I should monitor during this workload to evaluate its impact on server performance. Key Questions: 1. How can I determine if the workload of their queries is causing issues? What signs should I look for? 2. How many queries can be run in parallel without negatively affecting server performance? Is there a way to calculate or estimate this? 3. What are the most important statistics to measure during the execution of these queries? How can I compare server performance during the workload against periods without workload?