If your TV can handle PAL modes, then you won't have a problem. PAL is better at modes with lots of vertical lines (and a refresh rate closer to 50khz), like 352x288 for galaga & pacman. But this doesn't matter if you mount the screen vertically.
I have several cabinet, including two dedicated verticals with TVs as monitors (both Scart RGB) .
I use a 26" Loewe TV as a dedicated vertical monitor, and it rocks for vertical shooters like Twin Cobra and Flying Shark!
I also use a 21" TEAC TV vertically mounted into a classic-style low-boy retro cabinet (wood-grain finish). For some reason, classic era games like galaga, DK and 1942 feel best on the small screen! Vertical orientation on monitor is really good, lots of fun. Much better "feel" than playing galaga on a horizontal 27" screen.