Think i've settled on the DMSE route, just seems to make most sense. Now have got into my own head that it makes sense to spend a bit extra on the U6 Pro/Mesh.
The Mesh makes sense as it could just sit on a worktop, but then i think if i'm building from scratch and can ceiling mount the Pro in a decent location then does it make more sense to do that as it has less surface clutter.
EDIT - Got out my head. Went for the DMSE and U6 In Wall. The In Wall seems to make more sense, and i can mount it discreetly. Worst case, it'll be ideal in my office to provide Wifi and also a few ports for my latop etc and I'll be needing more units in the future, so if i decide a mesh works better than i can just re-arrange where things are.
A few random thoughts:
Unifi doesn't have to be all or nothing, you can mix and match to get the best results depending on your needs. For example, I use Deco mesh and a U6 Pro because mesh works well for me, but I need wireless VLAN support which Deco can't do, if I wasn't using VLAN, I would happily still be fully Deco. Switch wise I really like the Aruba 1930's as Unifi's pricing/features just don't make sense for me, and depending on the week you'll either find a UDMP-SE or a uSFF or desktop running OPNSense/OWRT/Untangle doing my routing.
By the time you deal with everything else, the 246 euro difference on this is going to look like a rounding error. You then need to consider if you can get a better NVR for similar money and are happy with the simplicity/limitations of Protect over say Hikvision/Dahua which do some very capable camera's for similar or even less money with full colour night vision/on camera processing etc. but better NVR's do tend to cost more, and that's before you add storage and camera's.
The UDMP SE has decent PoE support, single point of failure on the NVR HDD, but that's not uncommon in the lower end from any manufacturer, but the total combined uplink capacity between all of those RJ45 gigabit ports and the router is 1Gb, so all of them share that if going 'off switch' or if you have access to a faster than gigabit WAN connection in the future. It's therefore best suited to low bandwidth PoE devices such as camera's etc. That leaves the SFP+ port to connect to a switch, it's 1/10Gb, so you can either buy a switch that's 10Gb (SFP+) capable, or accept a gigabit uplink limitation again (obviously not a problem now with Star Link), or use an S+RJ10 module for 1/2.5/5/10Gb over copper in the future.
The Standard 16 is a horrible spec for the money. It's woefully under powered for a PoE switch (42w max over 8 ports upto PoE+) and again limited to gigabit uplink, the former is important, the latter won't be for now, but is worth keeping in mind that other options exist that are cheaper and offer way more power. A new Aruba 1930 24 port PoE+ is 195w of PoE+ and retails under £350 with 4xSFP+ (10Gb) ports, it's under £250 if you only want 12 PoE+ ports (195w) 12 non PoE and 1Gb SFP uplinks. that makes a Standard 16 PoE at £286.80 inc VAT (obviously I can't suggest where from as i'd break the rules and you're in Spain anyway) a questionable choice - do you even need a managed switch? If not and you still want Unifi, consider an Ultra.
I prefer fibre to copper for inter-building runs, in the UK it's the easy option to comply with regs (likely different in Spain) as it's non conductive, inexpensive, durable, not subject to the same distance/interference concerns, optics are cheap, as now are mixed media switches to break out from fibre to copper. What it absolutely won't do is PoE, so whatever is on the other end would require an injector or a PoE capable switch. This can get messy depending on the goal though and copper is easy/cheap.
While I would always run two cables to each room point, 4 to the office seems like an odd choice unless they are 2 pairs in different locations in the room? You can always plug in a switch for more ports, down side is single gigabit uplink, up-side is any traffic just on the switch is not going to be impacted.
AP wise it depends on the type of construction, you don't generally expect great results after more than one solid wall, so the 1-2 AP's inside is probably a buy one and see situation. I don't know Spanish building regs and all the construction I have seen is usually solid walls, so i'd assume the worst.
If you do go fibre on any of the runs, the cheap Chinese mixed media switches are great to break out to 2.5Gb copper and about £25-40 depending if you want to wait a week or have it 'tomorrow' over here, i'd imagine it's similar in Spain, optics can be cheap and DAC's are great for shorter runs/uplinks.
Curve ball on wifi - I quite like Deco mesh for the simplicity/money (I run both a U6 Pro and Deco's at home), but if you want to set a specific channel, you can't and it won't do VLAN and only guest and main SSID, that said extra port(s) and wired backhaul with decent hand-off handling and you can get 2-3 units for the cost of a U6 Pro.
