Oh right - that dual channel PCIe card is a solid choice. That should have better reach than a tiny USB dongle and is still well priced.
RE the "overkill" options, plenty of people have fast Internet that needs better than a basic wifi adapter. If you tried to use a 100mbps internet connection on that cheap tp-link you'd probably find yourself getting less than the 100mbps because the cheap wifi. That AC option to any half decent router would manage 100mbps no problem. That might not matter for 1080P youtube, but 4K streaming? File downloads/file sharing... then it matters.
Also, it's not just about Internet speed. Like lots of people I have a home NAS (network attached storage). Copying files around the local network is almost always limited by network speed. Try flicking through a photo library of high quality photos on your NAS over a slow wifi link... it's pretty painful.
Obviously lots of people don't care about that and just want their Internet to work, so for those people high end wifi products are indeed overkill. For those people who do want a faster connection, an ethernet cable is still better. But beyond that, there are people out there who really can benefit from an as-fast-as-possible network adapter and can't use a cable... that's who high end solutions exits for.
One more note, those more expensive solutions often have much better range too. So those with marginal reception can benefit from a higher end adapter even if they don't need the bandwidth (speed).
Not for your mum, obviously.