AP placement/mounting is key. https://www.emperorwifi.com/2017/11/antennas-why-they-matter-and-when-do.html
Cheers. Probably worth having 2-3 external ones then? Whats the reach on external ones? My garage is going to be built where you can see trenches dug out pretty much central in the image. Would something mounted externally in the correct direction there reach easily?