In answer to a question you asked, I do not know of any MAJOR changes to file locking mechanisms from Win7 to Win10, but there could be some complexity with changes to Trust Center. Microsoft CAN'T easily change locking protocols because so many non-Windows products emulate Windows File Sharing. If MS "broke" file sharing, users and 3rd-party vendors would raise a ruckus that would be audible around the world. However, the two versions of Windows would have different PATCH history. You would do your best to keep up with patching each system for as long as patching is available, though for Win7 I think that is mostly out of support status.
It might be useful to take some metrics on your Win7 and Win10 machines. Find one that runs fast and one that runs slow even though both are on the same (or approximately the same) speed hardware. Use Task Manager and select the Performance panel. Near the bottom of that you can select the Network display and see average or peak data rates. (The graphs are pretty but it is the actual numeric data rate you want, UNDER the graphs.) You might have to find a way to split the screens between Task Manager and Access so you can "do your thing" with Access and see what TM has to say about network speed. Run your app on each system. If the corresponding average and maximum network speeds are within a few percent of each other on the two machines, the problem isn't the network.