lsphp suExec has 3 modes: Worker, ProcessGroup and Daemon.
( https://www.litespeedtech.com/products/litespeed-sapi/php/guide-to-suexec-setups)
for your test, you can try Daemon mode, to see if any difference, and how compare with php-fpm.
for keep-alive setting, you can try LSAPI_AVOID_FORK=1...