I wish to know to and what changes... In PS4 at least I know the changes, I had the 3rd revision which was the best before slim and PS4 Pro, it had big improvements over the 1st one in regards to cooling and power efficiency.
Now I have the Pro 1st revision, don't know if they improved it further yet, but I have problems with it since the 1st week I bought it brand new

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I dare say the OP was heading more towards the sorts of understanding we see in the Apple world (
https://www.youtube.com/user/rossmanngroup/videos for an idea of the levels they are playing at). These sorts of people will notice if a resistor is replaced with a higher value one and then puzzle out why that might have been done, and also possibly if it is worth retrofitting to an older revision, as well as things like signals paths and all that. Most of the time it is Apple's sub par design and simultaneous expense (do I care if my 3 year old graphics card toasts itself? No it is probably out of date and a new one will improve games for less money than a few hours of diagnostic time. As Apple don't deign to use easy drop in hardware or sell replacements then yeah I sometimes have to consider binning/parting out a 3 year old Apple machine because a graphics card which now costs £30 for the same chipset on the PC has toasted itself) but it is what it is.
As far as game consoles go then you see it with some of the older "home computer" type things -- full specs and whatnot are available for the Amiga (not the best one but a start
http://amiga.resource.cx/models.html ), things like the BBC micro (
choice video) and more besides.
As far as what many in the US think of when you say console (was it made by Sony, Sega, Nintendo, Atari...) then I see some of the stuff in the audio-video world. However if you are concerned with that, especially if you are attempting to get the best possible quality now what was incredibly high end at the time is "you really want this? Thanks for freeing up the space in my shop/garage/attic/warehouse", then it is necessarily going to be analogue signals you are playing with, and thus for the AV paths at least you will be concerned with all the components of impedance and relative things, as well as small changes in voltage.