So the htop shows that all cores are maxed out.
I would like to see the full suricata.log to spot any other hints, also the amount of signatures loaded. Especially given the fact that pcre2_match_8 has a high overhead, which rulesets do you run and do you have custom signatures?
For a performance baseline you could also run without any signatures in a test to see if there is already a performance issue even without any signatures being applied to the traffic.