Based on the link below that compares the GT 720m to the Intel HD 620 (the Intel HD 4400 is definitely the weakest)... Overall, performance of those two are pretty close to each other with some exceptions. The GT 720m will perform better in GTA V and Metal Gear Solid V. However, the Intel HD 620 definitely performs better in Titan Fall 2, World of Warships, and CSGO.
Based on the video above Skyrim should run better on the Intel HD 620. The GT 720m gets an average of 32 FPS at 1366x768 and low settings. However, the video I linked above is 1366x768 with medium settings. Based on the FPS counter, the average FPS should definitely be above 32 FPS. As stated at the beginning of the video, the Intel HD 620 was able to run Skyrim with low settings at an almost constant 60 FPS though he did not actually record the game with that setting.