If doing Squats and RDLs I would do them on the same day. If doing regular Deadlifts I would do them on separate days. Regular Deadlift are more stressful, especially to the lower back. By doing RDLs instead you are focusing more on then hamstrings. RDLs are less stressful and easier to do following squats compared to regular deadlifts.
RDL, also known as semi-straight leg deadlift. You'll probably have some lower back soreness no matter how you do RDLs the first time. Keep the weight low, don't go to failure. Use YouTube for basic form. Key points: keep back flat, keep bar close to body, your spine follows your neck which follows your head which follows your eyes (if you look down your back will round...this is bad), the movement is all in he hips so DONT reach down with the weight instead reach BACK with your hips and stop when you feel a good stretch in the hamstrings.
Don't bench.
When you squat, break parallel. This means the hip crease is below the top of the knee. Look up powerlifting depth for squat. You should maintain a flat back and not let your hips roll into a "butt wink". For most lifters getting more than just breaking parallel would result in a "butt wink", which is none too healthy for your spine......we could literally talk for hours on how to perform a proper squat and techniques used to "fix" your squat, some of which are "bandaids" others of which are meant to improve hip and ankle mobility (most runners have poor hip and ankle mobility).
Alan