You won't "overtrain your CNS". As far as I'm concerned, that's a crock of shit for anybody but the most elite of athletes. And maybe them too. Overtraining your joints, muscles, tendons...sure, those are definitely possible, and within the realm of plausibility for people that think more is always better. But enough with this CNS shit.
As far as it interfering with leg training goes, there's a few ways to go about it. If you train legs once per week (give or take a day), you could do sprints after leg day, then again 2 days later, than 2 days later. That still gives legs 3ish days to recover before leg day in the gym again after the last time you do sprints. If you were to do them 3x per week like that, you'd probably want to keep sprinting volume per session pretty low. Or you could do them after leg day, then again 3 days later, so 2x per week. If you did that, you could afford to push sprinting intensity and volume up higher.
Ultimately, you'll have to try it out a few different ways, see what works best for you, and always be ready to make little tweaks to your programming as needed, and as you understand your body better over time, and become more advanced (hopefully).