As far as I am aware of, Eset's online scanner has all the features its installed paid version has in regards to file scanning. That would include heuristics, in program sandboxing, and the like. Assumed that would also include file uploading of any malicious detections since Eset uses those for analysis purposes.
Also note that heuristic analysis is most beneficial when analyzing executable's at startup time. Your only going to have that capability if you purchase the full Eset version that includes real-time, HIPS, Advanced Memory Scanning, Advanced Machine Learning, and Deep Behavior Inspection protections.