Both those boxes (2200/4400) are already at end of engineering support, and will go completely out of support in less than two years. What you can do with them under R80.40 (just as gateways - not standalone managed) will depend on which blades are enabled.
The 2200 is a dual-core Atom with only 2GB of RAM (non-upgradeable). Enabling more than just the Firewall and IPSec VPN blades (and perhaps APCL/URLF as well) will probably be unbearably slow. Would definitely not recommend doing any Threat Prevention on the 2200.
The 4400 is a dual-core Celeron with 4GB RAM. Most Access Control blades should be fine along with IPS (using Optimized Profile), much more beyond that would be pushing it.
HTTPS Inspection most definitely NOT recommended on either box.
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