It's definitely a thread-on freewheel. I was mostly wondering about the components playing well together. I've heard shimano and SRAM sometimes have compatibility issues. How would I best find out the BCD? Would it be stamped on it somewhere, or should I tame a Millimeter tape measure between two of the threads?

Putting a single chainring on there wont effect the chainline?

Thanks alot, you're very helpful!