The Zorro memory consumption can not be improved by a bridge version, but by using less series in the script.

The CPU usage by MT4 with 1.9 is indeed 30% higher - with Bridge 1.9 it's 5.5% CPU load, compared to 4.1% with bridge 1.8. This can be reduced on the MT4 side by setting eventsetmillisecondtimer() to a higher value, like 100. And on the Zorro side you could reduce the load with a higher ticktime, but that would not be noticable since the Zorro CPU load is normally in the 1% area.

Katalon did not work for us anymore since Sunday, unrelated to the bridge. We assumed their server is down. But we'll check that again.