Nesting Bird Boxes

I'm new to this site, so I apologise if this is the wrong area to ask questions of this nature (no pun intended).

I have a small-medium garden for an ex-council house (back garden is approximately 20m long by 10m wide, front is approximately 8m long by 10m wide).

I am interested in placing nesting boxes for a variety of animals, I know that hedgehog boxes go under the hedge at ground-level and spaced quite far apart, but do not know about spacing for bird boxes.

Obviously, I think, house-martin nests would go just below the eaves with, I presume, bat boxes at a similar height.

Is there any recommended spacing between boxes, or could I reface my entire house wall (above 2m in height from the ground) with different boxes and, in theory, get everyone filled?

Also, similar but separate note, will a Tawny Owl keep garden birds at bay?

I am tempted to place a tawny owl nesting box, but don't want to if it is a predator that will scare away other nesting birds and bats.

Again, new to trying to house wildlife - so I apologise if these seem idiotic questions.

Kind regards,