AdHearts is definitely a decent option, but if you're thinking there might be something better, check out https://bigspy.com/ and https://www.adspy.com/. Both offer robust spying features that let you track Facebook ads, see what your competitors are running, and get a deep dive into their ad strategies. BigSpy has a huge database and pretty decent filters to refine your search, while AdSpy is known for its fast search capabilities and wide range of platforms, not just FB. Another one worth considering is https://www.poweradspy.com/, which also gives you access to Instagram and Google ads, so it’s pretty versatile.
If you're looking for more advanced features or something that's a bit more tailored to blackhat strategies, sometimes getting the right VPN or proxy setup (like https://smartproxy.com/) can help keep your own ad research safe.