Regarding the specs of Montage classic, this article:

https://yamahasynth.com/learn/montage-series-synthesizers/mastering-montage-performance-basics-and-live-set-1/

Has a summary and claims each Part can have 8 waveforms (can an element have more than one waveform?  Hmm ...) and each waveform is 256 samples max which yields 2048 samples per Part.  

I haven't looked very long for an actual source but based on Montage M's 128 element architecture it would seem that at 128*256 would yield 32768 samples.   Not sure if there's some other limit but certainly the addition of 120 elements should give more samples per Part vs. Montage classic.  And I haven't heard of a resource pool limit to this 128 element architecture yet.  We'll see what Yamaha comes back with.

M limits are larger but the info you posted is incorrect.

In Montage M, do these limits remain the same?

No - the M models have almost twice as much user memory available and also have added 128 notes of polyphony for user waveforms in addition to the 128 note polyphony for preset waveforms that the classic Montage had.

The M models have 3.8GB of user memory while the classic only had 1.75 GB.

The M models also have 16 library slots while the classic only had 8

So both the amount of memory available for storing waveforms (and other user objects) AND the number of those waveforms you can use simultaneously has increased substantially in the M models.

In Montage, for the part dedicated to user samples, the maximum number of Waveforms (multisamples) that can be used is equal to 2048; the samples that compose them can be a maximum of 8192.

I'm not sure what you refer to in your question that 'that can be used' so while I wait for clarification from you I'll try to offer some info that may help clarify 1) available for 'use' when creating a performance/part, 2) available for 'use' when playing a performance/part and 3) amount that can be SIMULTANEOUSLY in 'use' when playing a performance/part

1) available for 'use' when creating a performance/part

All user waveforms/objects stored on the instrument are available to be chosen. If you have 1000 user waveforms you can choose a subset of ANY of them to use in a single AWM2/DRUM element. Each element can only use ONE waveform.

2) available for 'use' when playing a performance/part

Only the waveforms/objects you selected in step #1 above are available for potential use when playing the performance. You can't reference/use other user objects without first adding them to the performance. That can be effected using program change commands from a MIDI controller to replace a part with a different part that uses different waveforms/objects.

3) amount that can be SIMULTANEOUSLY in 'use' when playing a performance/part

That amount is limited by the polyphony of the instrument. For a classic Montage with 128 note polyphony it means that only 128 notes can sound at the same time.

CAVEAT: the can be a) 128 instances of the same note, b) one instance each of 128 different notes or c) any combination of the above.

The 'GOTCHA!' that is a common cause of polyphony issues is that a note will sound as long as its envelope is active. The note does NOT necessarily stop sounding just because of the KEY OFF event. Some envelopes are configured with long decay times.

1. a part with 8 elements my sound all 8 of them with each key that you play.

2. if you play a two-handed 6 note chord you are using a minimum of 48 notes of polyphony

3. if you 'pump' that chord 3 times quickly before the envelopes from the 1st chord expire you are using 144 (3x48) notes of polyphony which is greater than the 128 note limit.

So there can be, and often is, a HUGE difference between what you can configure and what you can actually use in practice.

The M models allow you to configure 128 elements for a single part whereas the classic Montage only allowed 8. But if that one part actually uses all 128 elements for every single key press you won't be able to play any chords at all!

If you provide some more specific info about what it is you need to do we can offer more targeted info.

In Montage, for the part dedicated to user samples, the maximum number of Waveforms (multisamples) that can be used is equal to 2048; the samples that compose them can be a maximum of 8192.

To clarify - you can 'use' all of the waveforms you create - but there is a limit to the number you can reference in a single part. And there is a limit to the number of those you can use simultaneously.

A waveform is comprised of from 1-256 mono/stereo samples. The size of a 'waveform' will depend on both the number of samples (1-256) it includes as well as the size of each sample.

The number of user waveforms you can create will be limited by the available amount of user storage you have when you create the new waveform.