I have a CCR2116-12G-4S+. My traffic levels are 3-4Gbit/s during peak hours.

My current setup is that I have my downstream and upstreams running on a single SFP+ interface using VLANs. No bridge - this is a core router.

Would there be any advantages (e.g. performance, lower CPU load, etc.) if I split this up to multiple physical interfaces? It would be trivial to do so for me.

For example, all upstreams on SFP+1, and all downstreams on SFP+2

Current Setup:

I have a CCR2116-12G-4S+. My traffic levels are 3-4Gbit/s during peak hours.

My current setup is that I have my downstream and upstreams running on a single SFP+ interface using VLANs. No bridge - this is a core router.

Would there be any advantages (e.g. performance, lower CPU load, etc.) if I split this up to multiple physical interfaces? It would be trivial to do so for me.

Well yes and no. No since there is still plenty of available bandwidth on the port. Yes as the CCR2116-12G-4S+ has a Marvell 98DX3255 switch chip with plenty of features including L3 Hardware Offloading.

By the way you may get some inspiration from Edge Router & BNG Optimisation Guide for ISPs and the related thread How to: Edge router and BNG optimization for ISPs here on the forum.