Couldn't find a satisfactory answer from google.
I capture hd videos off my canon camcorder as MTS files, I edit them in Vegas Video 15 and save them as masters as M2T files. WIndows 10 is able to make thumbnails and playback the MTS files not not the M2T masters. I can still play them back with VLC player but ideally I would like to see the thumbnails in file explorer as well.
I typically shy away from codec pacs as I have been told they contain bloatware or they do something else to slow your system down.