for shared hosting environment, you need suEXEC enabled. for dedicated server, it is ok to disable suEXEC and run opcache (EA, APC, xCache, etc).
for best security and performance, use suEXEC (and LSWS cache if you would like) in share hosting environment.
memcache is not opcache but in-memory cache to store keyed object and can be shared among different servers. memcache works with both suEXEC environment and non-suEXEC environment.