To Nios II/s or f processor speed

You can certainly try. I currently have 5 NIOS processors in a system running at 160 MHz and have had several run at 200MHz. The problem you will likely run into is meeting timing when you actually compile the firmware in Quartus. A lot of the peripherals will have a hard time running at these speeds. Onchip memory that is allocated using M4K blocks will have a hard time keeping up with these speeds. The FPGA you are using will affect this as well. But by all means, give it a shot.