Hi A. Chung and welcome to the forum. Everyone will have their own opinion, but I do believe in having layered protection. If you start looking at people's signatures in this forum, you will see some of the layering I am referring to.
Regarding a cloud AV, I use PrevX w/SafeOnline with no conflict with avast (make them both trusted exclusions). Additionally, you can also give yourself protection with on-demand scanners like MBAM or SAS, just to mention a few that most of us use. You can also use some handy add-on's offered within your browser to exclude scripting, LSO's, adware, etc.
I might suggest doing a search on this forum re: immunet to see some feedback others have had with the combination of the two software.
I hope this helps, and welcome again.