You should only use EWWW IO or LS for the image optimization, but here are my thoughts on which is better.
First off, I believe LiteSpeed only lets you optimize images 200 at a time, and there are some limitations in regards to fast/standard queue and quotas on the fast queue. EWWW IO has no limits on the number of images and you can do them all at once with our bulk optimizer.
But, Litespeed does let you use lossy compression for free, which would help you save storage space if that’s a concern. Otherwise, both do WebP conversion free, and if you signup for our paid plans, you get our full lossy compression for the best savings/quality ration possible (still with no image compression limits).