You could simply add a wireless access point and plug it into an Ethernet port of the home hub. That wireless network will have a different SSID and wireless password which you then use as a guest network.
It would not give total isolation from other devices on your own network, as that would need a router designed to do that as part of its internal software.
Some Netgear routers have that facility.
If you do it that way you will need to make sure you do not have network sharing turned on on your devices or your guests will be able to access those files.
Ah ok that would do, can you suggest one? That would do. It's only temporary for when friends come etc. I don't really want to give out my password, rather give a guest account.
You would need to buy a separate wireless access point like the TP- Link TL-WA801ND and connect it to a spare Ethernet port on the home hub, once its been configured. It works very well, with a good wireless range. Make sure you configure it correctly.
This can transmit up to four different SSIDs, each with its own password and MAC filtering options. Normally a single SSID is sufficient.
These are the network settings I use.
Not sure, you would have to see if any of the Apple users offer help. I would however be concerned if guests had direct access to the Time capsule, as it may be a security risk.
The TP Link would be simply left connected all the time. If you use the Multi SSID option, you can in fact setup additional secure wireless networks for you own use. It helps to reduce the loading on the smart hubs wireless network, as some devices could be registered to one of the four TP Link SSIDs.
It can be connected to the remote end of the powerline link.
One of the SSIDs would be reserved for guests, the rest would be free for your usage.
I have set up a Guest Access with TP LINK much the same as you have suggested on the other end of a Powerline Link, but can't see an option to alter TX Rate, although there is a drop down option shown on User Guide. Wondered if the same applied to your TP Link?