Ok so many thing's going on in this thread
First for the whole sound question, I am not a sound engineer or anything so if you really want to know the difference in more detail then there are websites with actual sound engineers who explain everything in detail.
The onboard "Sound Card's" are utter trash, they are the bog standard basic stuff efforts of a "Sound Card" that the manufacturer can get away, until you get the "High End Motherboard's" when generally they will have a slightly better setup but no where near the level of a "Good" sound card.
Going for a "Good" or "High End" internal sound card will allow you to hear thing's in music, games and film's that you probably wouldn't have heard before potentially without messing with Amps and the EQ if the software has one.
The Creative card that I have does not have a EQ so I have to use 3rd party software called "Equalizer APO" combined with "PC Equalizer" which is a GUI for "Equalizer APO" and this then will allow me to tweak my audio for specific games etc.
Now for "External Sound Card's" these from everything I have seen and some people I have talked to are the "Best" solution if you want to hear games, Music and Film's the way the creator wants them to be heard.
The headphones is personal choice though, I have the "Beyerdynamic DT 990 PRO" they are nice headphones, but the only thing they are lacking in for me is "Bass" and although I say it's lacking that is because I like a lot of "Bass", and if I wanted I could change them but to be honest once I have a new sound card at some point in the future I may look at changing them, but to get a set that should meet what I want I could be looking at up to £2.5k for the headphones or just £100 it depends on what I want.
This is the thing, my mum doesn't care about 1080p tv's or 4k tv's because she say's she cannot see any difference between SD and HD images, to the point that you put a channel on the TV that is not HD and then put the same channel in HD and she will say they look identical.
That is how it is for people with sound, when playing PUBG with Bop he will hear things long before me unless I mess with my sound setting's because the hardware is different and designed for different things as well as Bop having what seems like super human hearing
Now the Motherboard query from Rammy.
The X570 motherboards and STRX4's are all PCI-E 4.0 capable motherboard's, and the chip set produces a decent amount of heat because of the power used for the chip set, so they need the fan only if you don't have decent air flow in your case.
Right now whilst typing this the one on the motherboard I have is not spinning, and even putting Cinebench running doesn't cause it to spin.
If you are concerned about the little fan, then as Paul said you can watercool the motherboard but the one he showed in the picture is about £900 for that motherboard so yeah not cheap, but it is one of the best motherboards on the market for AMD 3000 series CPU's.
If you buy a cheap board, then you might have issues later down the line but if you buy one that is set out decently then you should be fine.
