Avira you can install now only the antivirus and is very light on system with low ram. The bad is the ads only. For CCAV and Forticlient agree with you. Sophos Home free very huge ram usage. If i remember good the last time i tried it is aboot 300, 350 MB!!!1. Avira I wouldn't touch with a barge poll, even it's VPN is bloat on the system. Avira installs it's own PUP which takes up even more CPU usage and something I would stay clear off, but this is just a personal annoyance of mine when I have tested this product in the past.
2. Zonelarm's Free, features for the AV is limited, barely any protection for phishing type attacks and their Firewall is very heavy at 150MB when compared to Comodo's equivalent
3. Huorong's suite is a new product and I wouldn't even test this as a MWT user myself until there is enough suitable knowledge to know about this product, however there is a thread detailing bits and pieces about this product, it's worth a shout..
With my suggestions, it falls in line with your light thesis and they have good protection.
1. CCAV: Can load your web browser within a sandbox, great solid protection, also has in built settings you would to enable that would stop sandboxed processes from connection to the internet, stopping personal data from escaping.
2. Sophos Home Free: Great signatures, Sophos also own Hitman Pro! Did fantastic in tests I did against this.
3. Forticlient: Has an in built App Firewall, fantastic web browser based protection, even for phishing, something I would recommend! Many companies also use Forticlient, so you can be sure the signatures can be great too!