Hello, Greetings.
Lightspeed cache is Cache Mechanism suite which includes several features such as Object Cache [memcache/redis], Minify CSS, JavaScript, and HTML, etc.
Memcache is Object Cache Mechanism which is to store previously executed database quarries in order to reduce query execution time for upcoming database quarries.
Assumption = You are using WordPress or Joomla CMS.
Wish to use :
https://wordpress.org/plugins/litespeed-cache/
If I am correct, then...
When you enable Lightspeed cache plugin along with it's memcache feature; it would be more beneficial.
Note :
You should not use Lightspeed cache plugin along with memcache plugin; i.e. If you wish to enable lightspeed cache plugin ... first disable and de-activate previous memcache plugin.
Also, make sure that your hosting account has Lightspeed web server[Apache]; else lightspeed cache plugin will not deliver best results.
some features are like double edge sword; be careful with features that you choose to enable/disable.
Regards