I might suggest moving to 30 Napatech streams (and hence, 30 suricata worker threads) and adjusting the memcap values down. 200GB for reassembly is far too high, imo.
Is the traffic “well-balanced”? To determine if it is, you can use the “profiling” tool (from napatech) that shows traffic distribution to each stream. You should see balanced traffic. “monitoring” will show traffic by port as well as traffic packet size distribution.