Do native speakers of major English varieties actually say "a software" or "softwares"?
'Software' is non-countable (like 'milk'). As a native American English-speaker who grew up with software (and a vested interest in it) and is nearing age 40, it seems like people who are quite computer literate and have been since before the age of smartphones will never say 'a software' or 'softwares' unless they're joking, or mis-educated, but native speakers (including business managers/owners who aren't personally into computers) do say this sometimes (much to the dismay or amusement of those who know better, such as the programmers who work for them). People who aren't into software much or who don't really know what it is have been known to erroneously say 'a software'. The younger generation, and those who started using computers at the same time, are probably more prone to misusing the terminology if they use it, since it's less common these days (they usually say 'app' instead).
'Softwares' seems to be less common than 'a software' by far, for native speakers. But, regardless of who says them, 'a software' and 'softwares' are incorrect usage—kind of like how 'a women' is incorrect and 'women' or 'a woman' are correct (I have no idea why people keep writing that, unless it's autocorrect doing it).
Instead of saying 'a software' you should say 'some software', 'a program', 'a computer program', 'an application', 'a software application', or more modernly, 'an app' (although if you're talking to an old-time computer techie, you should probably only use 'app' if you're talking about mobile apps, since they didn't grow up with that and the term became popular in the smartphone community, which wasn't always everyone).
Instead of 'softwares' you should say 'software', 'programs', 'computer programs', 'applications', 'software applications', 'apps' or such.
It should be noted that software is a much more general term than 'program' and all those other words I listed. Software can refer to programming libraries/modules, media files, and other stuff (not just runnable programs—although as you'll note in the comments, not all definitions of software are so broad as to encompass things besides programs). Anything you program as a computer programmer is software. The same is not true of the other terms. Even a chunk of code that does nothing by itself is software. Documentation for programs is considered software. Even files are software (for instance, images, text files, documents). Images and word processor documents may be software, but they're not apps, programs, etc. Everything that is stored on a hard drive is, in my opinion, software (although some, if not many, people might contend that point, and think that software has to give more direct instructions, or be part of something that does in order to be considered software). Even websites are software (but please don't call them that; just call them websites). Computer programs are things you can run and use directly (like OpenOffice, Firefox, Audacity, SynthFont, VanBasco's Karaoke Player, etc.) Computer programs are also used to open files (if they support them; like, VanBasco's Karaoke Player can open and play .midi files—but both the midis and the player are software, while the midis are not programs).
As a native American English speaker with lots of family who are native British English speakers: No, neither of these uses are common in AmE or BrE (I can't be certain of Australian English, but I highly doubt these are commonly used there either), however there are specific instances where they are ... not necessarily incorrect. That doesn't however mean that it's a good idea to use them.
For the first portion of your question, regarding "a software", this is likely never correct (I suppose there may be an exception or two, but I doubt it), however "a 3D software" (as is said in the linked YouTube video) is acceptable. Why? Because you're not saying 'a software', but rather 'an individual piece of software, among a type software'. In most cases however, there are better ways to phrase this. Generally these include "some software", rearranging the sentence, and/or switching to a countable noun (program or application).
For the second part, I'm going to step away from the word "software" for a moment to another 'uncountable' word that is easier to explain with: "people"
"People" is any number of people other than one, because it generally acts as the plural form of "person", however it can also mean a group of people: "a people".
There are many people on the earth, and you can refer to them all as "people", e.g. "Many people live on the earth" however the Egyptians can be considered 'a people', and the Japanese are also 'a people', and there are many more 'peoples', if you refer to multiple of these groups of people, the correct term is 'peoples', e.g. "There are many peoples living on the earth." This sentence is not saying that many individual people live on the earth, but rather that there are many groups of people living on earth, each of which can be considered as 'a people'.
The use of "softwares" that you see in the linked YouTube video is not identical, but similar in that it is not actually referring to what you may think at first. It doesn't mean one piece of software (e.g. 3D Studio Max, FreeCAD, K-3D, etc.), or software in general (e.g. "I develop software"), rather it refers to multiple individual examples of a group of pieces of software: 3D software, not as a category, but as the individuals within that category. FreeCAD is "a 3D software", and K-3D is "a 3D software", referring not to the group itself, not to any specific individuals within the group, but rather generic, but distinct individuals within the group, you can say "3D softwares" i.e. "There are multiple 3D softwares available for free." however, again, despite this being "not incorrect", it's usually a bit awkward, and should generally be avoided.
I apologize for the awkward descriptions of how these may be used. In my defense, while they are "not incorrect", they are awkward uses, and usually are not the right thing to say.