ok... The higher limit u have, the speed u connect more faster ( Means that bitcomet connect peers more faster / IE also can be loaded faster) ... but it won't boost up "download speed" of bitcomet. The download speed depends on ur configuration such as "portforwarding, firewall......."
Even ur max half-open connection is 10, it only take a little bit longer time to connect and later u also will achieve the high speed which base on your configuration... (Don't worry, it won't affect the download speed of bitcomet).
Note: the higher limit u set, the higher health risk u have....
If i got wrong, please correct me