RF is actually a general abbreviation for 'Radio Frequency' so technically they are all RF 
In answer to your sonoff question.. @ericm has developed some sonoff drivers - have a look here:
I'm in the UK too and there are less devices available to us compared to our friends across the pond in the US
I use a lot of the Philips Hue stuff either connected to their bridge (bulbs & LED strips) or directly connected to HE (motion sensors - both internal and external)
You can also look at the SmartThings devices (motion sensors, door contacts, sockets, leak sensors etc) most, if not all, will use in-built HE drivers and are solid and reliable (at least for me)
Although the devices I use are not the cheapest, they have all been reliable for me.
(Which for me is more important!)
Andy
