CPU vs Memory Usage

A back in May 2020 I found that the PHP-FPM processes were consuming 96.5% RAM and 3.3% CPU. But today it is flip flopped. CPU is getting near 70% and RAM at like 2.6%. Note that all the resources of the server were applied to one website that uses Woocommerce and everyone is adding a product to the cart and checking out. Here are the configurations.

May 2020 Ecommerce Event:
Visitors: about 800
Ram Usage: 96.5%
CPU Usage: 3.3%
Type: IONOS Dedicated Server L, Centos 7, MariaDB, Plesk, nginx
CPU: 4 Core x 3.5 GHz (E3-1230 v6)
RAM: 32 GB
SSD: 2 x 480 GB Software RAID 1
PHP-FPM Max Children (plesk setting): 350
PHP-FPM Max Requests (plesk setting): 400
PHP-FPM Control: Static

Feb 2021 Ecommerce Event:
Visitors: about 650
Ram Usage: 2.6%
CPU Usage: 70%
Type: IONOS Dedicated Server XXL, Centos 8, MariaDB, Plesk, nginx
CPU: 8 Core x 3.0 GHz (Intel Silver 4123)
RAM: 96 GB
NVMe: 2 x 1000 GB Hardware RAID 1
PHP-FPM Max Children (plesk setting): 1000
PHP-FPM Max Requests (plesk setting): (not defined)
PHP-FPM Control: On Demand

Any thoughts on what is happening? Is WordPress or Woocommerce modify their code to help with the earlier memory consumption to only trade it with high CPU usage? Or is not defining the Max Requests resulting in much higher children being replaced and thus higher CPU load? I’m hoping someone can shed some light here. Thanks in advance.