90% of weird noises can be fixed by increasing buffer size.
Track dry, or use direct monitoring on the focusrite with the record monitor disarmed in reaper.
Most computers can handle that @128 bit buffer or less (on my audio rig, i7, 6Gb, texas instruments FW, I track at 48 bits with no problems). Later, when you start to add VSTs and plugs, weird noises will happen. Increase the buffer size; latency will increase, but you dont need it any more, since now youre mixing, not listening back to anything thats supposed to be real time.