Office 98 still used MSVC++ 4.0 hosted on x86 (the Cross-Development Edition that targeted 68k/PPC MacOS). They migrated to CodeWarrior for Office 2001.
Until someone with a better memory and more direct knowledge comes along, I'm going to guess that they used Apple's tools. In the early 2000s, I know that's what they used because I had buddies over in the Mac BU.
I can't answer the compiler question specifically, but based on using some of those products (at least Office 98), I think they ported a fairly large subset of whatever API they were using on Windows. Most of the controls were almost identical to Office 97 on Windows, except for things like the Mac menu bar. Office 97 also allowed the customization of the order of menu bar items; the Mac version retained these options, but they never actually worked.
At least in the Word 6 et al timeframe, Microsoft had switched to developing their Mac software using the Visual Studio Tools for Macintosh cross compiler running on Windows. They switched back to doing development on the Mac for either Office 98 or Office 2001, using Metrowerks CodeWarrior.
Not /strictly/ nobody - the 3DO version of The 11th Hour was crafted under MPW, using Norcroft C. But yes, CodeWarrior certainly dominated, particularly as the 90s closed.
Obviously, I meant Joel Spolky's definition of "nobody" - Please understand that I'm talking about large trends here, and therefore when I say things like "nobody" I really mean "fewer than 10,000,000 people," and so on and so forth.
Strictly speaking wrt this definition, if MPW had 10M users, it would be a runaway success. But nobody cared, even when it became free.
If you used MacApp, you had to use MPW! I worked for a company where the president read an article about MacApp and as a result made us switch to MacApp. I learned valuable lessons in how to never ship software from that company.
Blog posts from MacBU employees that you will find interesting (also their archives around this time): http://www.schwieb.com/blog/2006/06/02/a-brief-history-of-ma... https://blogs.msdn.microsoft.com/rick_schaut/2006/06/03/the-... https://blogs.msdn.microsoft.com/rick_schaut/2004/02/26/mac-... http://www.schwieb.com/blog/2006/06/04/pseudo-code/