Hi @Roland_Alden,
Thanks for joining office hours & posting here 
The connection key value pairs aren't Retool specific features. Your resource should have connection options listed in their documentation (i.e. different options you can include in your connection string).
As far as connection pooling in Retool, I will refer you to this community post that recommends putting a connection pooler in front of your database so that you can manage and limit the connections. Connections are generally freed shortly after the query completes, but if you have a lot of users or queries being run simultaneously, you may run into a situation where a large amount of connections are opened (a max of 5 would likely be too low).