Hi Mike, if you dont mind me saying I think you are going about teaching yourself rendering the wrong way. You are tasking yourself with being an Architect, Landscape designer and renderer. All arch vis guys I know work from archirects plans and elevations or in the case of more arty personal projects "mood boards, or/and reference images (lots of them) At art school visual artists in just about every discipline have walls or desks full of references. Old school oil painters use a reference, being a real landscape and do pencil sketches of rock formations, that might be called a "study" it is not plagerism.
If you want to do a pool courtyard firstly identify what type of pool courtyard, minimalist, funky, period, art deco then collect lots of images you like in the genre and study them, perhaps try to do a render and try to copy the whole thing, lighting, Architecture, sky type. Then study water levels associated landscaping and plants, of just mash elements together, tilling paving, water levels pool lighting placement and effects.
I have attached some examples of a study I did a while ago, you may note that I did not copy verbatum not that there is any thing wrong with that. And an example of a mood board
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Mood board Credits to: jeremyryanjonathan (CG Architects)