[Quoth]

I've a 3m USB-A to USB-C cable and micro & mini adaptors for it. Very handy.

I can find no difference in charging or speed using USB-C to USB-C for PC to Sage or Elipsa or Lenovo Yoga Tab compared to USB-A to USB-C, and actually the Sage charges fastest with the supplied Lenovo USB-A charger (though the tablet is USB-C). Also makes no difference using USB 2.x or USB 3.0 speed USB-C or USB-A ports to a Sage. The two fastest USB devices I have (A USB 3.0 HDD and a mini-USB interface camera) go no faster on USB 2.x than USB 3.0, so I'd guess only an NVMe over USB SSD and maybe a SATA SSD over USB might go at USB 3.0 speeds. My Firewire based Digital Camcorder goes faster than any USB device I have.

There are also USB-A data/charge cables with micro-SUB, mini-USB, USB-C and Apple Lightning tethered adapters at about €12.

Really only USB-C monitors and USB-C laptop PSUs need USB-C to USB-C cables. The cheap set of dumb USB-C host adaptors I have allow mini-USB, micro-USB and USB-A plugs for Tablet to host slaves.

The "advantages" of USB-C for a phone, tablet or ereader are purely the connector goes in either way.

Advanced features need advanced OPTIONAL features at both ends:
1) serial data for power supply negotiation, up to 20V, so as to power a laptop, except the max power isn't enough for gaming laptops or multiple downstream charging.
2) Video. It actually needs extra signals and quite a few laptops and most tablets/phones with USB-C can't drive video to a monitor with USB-C only. Make sure any monitor has at least HDMI.
3) Swapping Slave and Host mode. Like USB2Go on mini-USB and micro-USB, not all USB-C ports do it.
4) Charging and being a host port at the same time. Rare. And actually a few rarer phones/tablets with micro-USB can do it too. Both often need a Y cable.

Basically USB-C "OPTIONALLY" combines a power connector for more than 1.5A @ 5V, HMDI video and everything a micro-USB does. It seems to me a pointless design that sows confusion and underspec'ed to power more powerful laptops.