It's unlikely that the car will come with the latest softeware, unless you specifically ask the dealer to make sure its on 56.00.513.
I had a replacement BT/Wifi unit which came with version 230 only recently, but installed 511 version myself, although its not recommended to diy. I just got sick of going back to the garage. Dealers i've found are pretty unhelpful.
I have no issues with the entertainment, unlike the last version in my 2013 car, where the usb always resumed at the first track, navigation of the system appears to me as first class. I would say that BT streaming is probably the weak link, but that's probably due to my phone.
The nav isnt great but works usually. You can carry out a update after 62miles via toolbox also do a backup and copy that to a spare card if you want. Wifi can be connected at anytime after the nav has started and you can select which signal to use, however my 100M range router will not reach to my garage or drive, possibly from the road but i never leave it there so don't know.
I also don't know if it defaults to the last used wifi, but BT will connect to the last used phone if you have more than one paired and in range.
I'm still learning myself in some areas, but i'm happy with the functions i use daily, there are a few utube vids worth watching, and lots of information on mazda247. The usa doesn't have wifi however, so don't assume everything is applicable to the UK.