I am unsure of what you are trying to achieve here. The number of web server connections include any HTTP(S) connection to the SonarQube Server: users browsing the UI on the browser, Web API calls, and of course analysers.
If you have 50, 75, 100 or 200 scanners sending their report at the same time, the Compute Engine will still “bottleneck” by processing one at a time.
To be technically precise and answer your question: no, the maximum scanner instances that will be able to connect at the same time will be 75, as you need to take into account the queue (acceptCount=25). But this is if no other connection is open with the server at that time.
Now again, this won’t play any real nor worrying role in your use case as you only have 1 CE worker, and not all scanner analysis will send their report at the exact same time. When it comes to the Web Server, the default settings should be fine.
To achieve your original goal of increasing parallel processing capacity of analysis reports by the server, you’d need to upgrade to at least Enterprise Edition and increase the number of workers.