Hello. I use both Better WP Security and W3 Total Cache. No problem so far.
But I disable these things because they require lots of memory and CPU resources (at least on my tests):
- Menu > Security > Database Backup
- Menu > Security > Intrusion Detection > File Change Detection
- Menu > Security > Ban Users > disable Enable Default Banned List
I disable Default Banned List not because it slowdowns my sites but because I don't see I need it and because it will put long list of blocked IPs on .haccess file which I think it might slowdown my site a bit.