i cannot help you with tips for rendering, but what makes this villa a little bit unrealistic, for me at least, is that it lacks some real world features, that i personally would want to have on a house. And it´s usually those small details, that breaks the illusion.
Most striking thing was that the roof have no gutter, no side of the roof have any way of collecting rain water and redirect it to somewhere else. Not sure, how often it rains in that area, but i guess, such a thing is always handy.
Another thing is some stuff, that i find… impractical, maybe personell taste, but yeah:
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at min 1.40, that glass door, how is it intended to be opened? I cannot see any handle for either swinging it or pushing it sideways. I would not want touch such a nice glass door with my bare hands, would get dirty way to fast.
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at 1.50, that window above that glass door, in the middle of nowhere. While it looks nice, how would someone get there, in case of cleaning, opening, closing or repairing it? It´s literally out of reach from any side. Even the stairs cannot be used, to far away. a ladder?
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at 1.57, those stairs look a little bit narrow, and i would love to see some metal poles etc. for reinforcing those glass banisters. And something to grip on on their top, maybe a wooden rail? You don´t get much grip on a slim glass wall, and again, touching glass…
(also i hope, that this will be heavily reinforced glass, accidents happen, and banisters are there to keep people from falling sideways from the stairs. Unless thats armored glass, then this will shatter, and cause even more injuries, if its not safety glass (and as far as i know, safety glass is not intended to stop people 
) Several of my fam fell down some stairs, and believe me, if i say, that falling people generate a lot of force. -
at 2.20, those lightbulbs over the area with the stairs, same challenge as the window, that hangs in nowhere. Just in case, that one of those lights have to be repaired, how would you get there? Also, light switches or whatever they use for controlling the lights? Where would those be?
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at 3.30, again glass doors without a handle or door knob. Cleaning glass is not that nice
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and at the outside, their wooden doors, that should cover them, could have some hinges
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and maybe as small extra, hide a power supply to that nice frame with those climbing plants. Looks nice at day, could look nice at night with some fairy lights wrapped around ^.^ Could also light up that place at night, since i cannot spot any outside light source for enlightening that place and pool, or any part of the house and way to the pool and garden. A night shot would be interesting to see.
Have a nice day