You don't have to use SFP to connect switch and router, you can use normal ethernet cable.
CRS have dual boot option, so ROS or swOS but with only single core 800MHz CPU im not sure how well it will handle routing at higher speeds, especially if you start to add firewall rules etc.
I would give swOS a try, i personally use mikrotik switches with sw os and swos lite at work and home and im happy with them.
One minus is that you can't configure swos from winbox, only webfig. But winbox can discover them.