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.
That's not at all what I'm seeing. I'm seeing ~20% CPU usage on bridge 1.8 and >100% CPU usage on bridge 1.9. Two instances running bridge 1.9 bring my server to its knees. Far more than a 30% increase.
