I see a host of problems in your future. The space to screen the pool equipment is tight and you are not being realistic about the future size of the arborvitae. A tree at the fence is going to encroach on the pool as it gets large enough to provide privacy. I think I'd relocate the arborvitae to the fence and screen the pool equipment with a solid panel. Shrubs, ornamental grass or something along those lines could temper the end of the panel.

At the first picture below, it seems the arborvitae is going to do little to screen off the width of the objectionable view beyond, or give privacy back from the same view. Small flowering trees made of large shrubs would give more interest. They'd still need some other shrubs (like those hydrangea your neighbor has) outside of the fence if you want privacy.)

Lovely backyard setting! I agree with Yardvaark regarding the arborvitae around the pool equipment. They're small now, but they won't stay that size for long. I'm not a fan of tree plantings near pools due to the mess. Besides, the screening benefits won't be realized until the trees mature. Perhaps a patio with a pergola to screen the view:

Examples of pergolas:

The pergola wouldn't need to be huge to give you the screen from your neighbor's window, if strategically placed.

Some ideas

as to plant suggestions .....z6 is about half the US ... and quite divergent..

a little more specificity might help ... big town name good enough ...

ken

Comment:

I agree with ken_adrian, zone 6b covers many parts in Canada and the USA; having a specific location such as the city will help in identifying what plants will be favorable there. Also, I would suggest building the pool fence just a little wider than your pool size. It will increase privacy and beautify your pool deck.

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