Yes, the monitor will accept 15KHz, 25KHz, 31KHz or what ever to produce the correct resolution for each game, as long as you have your MAME and ArcadeVGA settings right.
The NEC Multisync XM29 Plus is basically a very high-end arcade and PC monitor.
If you possibly can, check out the monitor before you buy it, play with the controls, display some games on it. Some of the monitors I have gotten suffer from geometry or convergence problems. These issues are usually only noticeable in Windows or what ever. When displaying the games, the are much less noticeable. But that may be the case with a lot of big CRT monitors, even brand new arcade monitors that you buy from WG, Billabs, or whatever.