2. I want to drop as many cables in the stud wall as possible to future proof the outlets I’m going to connect to it - I will currently want to connect a Sky Q UHD 2TB, PS5, Sonos Beam 2 or Arc (undecided) Amazon fire stick HD. What do you advise I drop down the recess?
HDMI cables - make sure they meet the latest
HDMI 2.1a specification. They should be 'Ultra High Speed' (8K@60 / 4K@120 / 48Gbps) by the looks of it. Deciding on what you want to use for external sound may dictate how many HDMI cables you need to drop down the cavity. If using an AVR equipped with ARC or eARC (for example) then you may only need the one (provided you get one with sufficient HDMI inputs), but the AVR would need to support all the features offered by your PS5, otherwise you might need an extra HDMI cable from PS5 to TV for that. I don't have a PS5 myself though, so make sure you read up on the best connectivity options. If you go for a soundbar, then you'll probably need to drop as many cables down the wall as you have external devices, plus one for eARC to the soundbar. Make sure they're all more than long enough to reach your sources, but don't go overboard as resolutions like 4K@120 (even on a supported cable) will only work a certain distance reliably. Check possible cables routes for length with any old cable or even a piece of string !
Optical (toslink) cable - consider having one of these as an alternative to use in case eARC doesn't work reliably. I don't have too many issues myself, but many people resort to optical when having ARC/eARC problems as reliability/compatibility between a TV and eternal sound system is never guaranteed.
Power cable - do you have an electrical socket behind the TV ? If not, you'll need to consider where the TV will plug in. Many people have problems when it comes to upgrade time if the power supply cable for the existing TV is buried in the wall and/or difficult to remove, so I would plan for this.
Coax for Freeview/Freesat tuners - you may have Sky now, but what if you ditch it in the future ? Buy good quality, foam-filled coax (not cheap hollow-core RG6) and keep it as far away from HDMI cables as you can to minimise the risk of interference.
Amazon Fire TV Stick - this is a tricky one as it'll become fairly inaccessible if plugged into the back of the TV directly. You could consider the use of an HDMI extension cable to get it to a more convenient location or plug it into your external sound system if it has available HDMI inputs. Don't forget it'll need it's own power supply wherever it's located, so factor that in. If you're a Netflix, Prime or Disney+ subscriber, you should really go for one of the newer 4K Fire TV Sticks to get the best from a 65" OLED but, thinking about it, you'll presumably be able to access most of the apps you're likely to watch directly via webOS on the C1 anyway.
USB - think about whether you're ever likely to want to plug in a USB stick for watching movies or viewing photos. If so and the TV's USB ports won't be accessible when on the wall, you could fit a USB extension cable to get a socket to a more convenient location.
Lastly, if you're really wanting to futureproof this set-up then I would try not to trap any of these cables - try and make it so they can be easily removed or replaced in the future. Creating some kind of channel for this without obstructions or sharp, awkward 90 degree corners is the way forward - you can use electrical conduit (or even something like fixed or flexible DIY waste pipe !) to make this easier or simply factor a channel into the design of the stud wall (ensure there are no batons in the way).