The A3000 (68030), A1200 (68020), A4000 (68030,68040) and CD32 (68020) were all 32-bit. The other models were 16-bit, but (with the exception of the A600) could receive a 32-bit processor upgrade.
Technically already the A1000 was a bit more than only 16bit. The internally 32bit wide registers on the MC68000 CPU helped with speed/coding, even though the system around it was only 16bit.
On the other hand, despite being 32bit in general, the later big-box Amigas you mentioned were limited to 8bit audio (pseudo-14bit with some code magic using channel merging), unless you plugged in some dedicated sound card and installed 3rd party software. IIRC PAULA (the audio chip in the Amiga) stayed the same (functionally) over the whole lifetime of the Amiga series of computers.
Rumors have it that the blueprints and/or source code (of PAULA) got lost, so C= could never develop it further without risking to break compatibility. Unlike today, back in the Amiga times it was usual to bang the hardware directly instead of using official API's for speed reasons.
That made games and demos look good on early machines, but eventually was a nail in the coffin, as lots of development was guided by that "compatibility mandatory" mantra enforced by C= management, which ruled out significant improvements to the hardware that could keep up with the competition left and right.
But without officially supported(!) better hardware, software developers did not see the need to make use of what was available (be it the smaller steps from C= itself or the various 3rd-party approaches). And without more demanding software, why develop the hardware further ...
At least in this respect Apple does better than Commodore: If a new hardware breaks compatibility for good (agreed: debatable) reasons, Apple is not shy to enforce it onto the customers. Even if it feels a year early to the customer. Maybe they eventually learned
something from the history of the Amiga!
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my first real exposure to OSX [...] thinking that it was as close to the Amiga experience as I'd had in years.
Same with me. Very big part of it was the design language of OSX with the Aqua theme. Definitely different from the rather uniform Windows approach and feeling like an advanced bigger brother of the Amiga UI. Very sad to see the Mac (and iOS, for that matter) going back to flat, symbolic icons (often monochromic) and other UI elements, that scream "boring" instead of "fun" :-(