I've found most montis (at least the ones I've grown) to be practically bullet proof. Even when most of my expensive acros were dying, my montiporas doubled or tripled in size.
I've also found that the faster the growth rate of the acropora, the faster they are damaged by unfavorable swings in parameters. My slowest growers have all survived my year of tank hell relatively unscathed.
As others have said, stable alk is absolutely critical. How you do that doesn't matter, but if you dose by hand you would need to have the diligence and attention of a robot to keep up with it with even one or two good sized colonies in the tank. A few days of neglect can cause damage that takes from a few months to a year to fully recover from. A doser or calcium reactor is critical IMO.
As a general rule - the more expensive the specimen, the faster it will die if something bad happens. Probably the main reason there's still a difference between "designer" acros and the more common things everyone has.
Finally - I think you're better off going straight to the things you know you want than filling your tank with "learner" pieces. Montipora capricornis is a great testing coral, but it can become as weedy and annoying as the ugliest of mushrooms, and it's next to impossible to remove. At the least, don't put tiny frags of it everywhere in your tank because you can't bear to throw the pieces you accidentally break off out. Be ruthless.
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