I just ran the game borderless fullscreen successfully with Borderless Gaming, Fullscreenizer and Windowed Borderless Gaming and they all worked (main menu is messed up though so you have to load a game first). With Windowed Borderless Gaming, there was a small cursor flickering issue so I wouldn't recommend using it for this game.
You don't need DXWnd to run the game windowed and you must run the game in 16-bit color mode (on win10) to fix the flickering purple cursor. You can use http://dualmonitortool.sourceforge.net/ to lock your cursor to a single screen.
Check this link: https://pcgamingwiki.com/wiki/Dungeon_Siege#Video_settings