for some reason I cant mark up the pic. essentially I would do this...
1.5 in homerun line to each 18" sheer
2" homerun to the 48"sheer
2" homerun of 3 seperate lines for the returns. I would T off to 1.5"and stack a pair on each 2" line. I would seperate the returns to not be next to eachother, like every other one. reason being if you ever had a leak and needed to shut down the line, its better for flow to be missing returns in between
2" homerun to each bubbler.
for suction I would have 2" homeruns from each skimmer.
for the strip drain I would have 2.5" or 3" depending which drain you used.
The spa is its own deal its up to the PB what plumbing and jet setup he is going to use. i dont rly build concrete pools and spas, the rare occasion I do an attached spa its a shell raised on pool edge and simple plumbing
the sheers and bubblers all running at the same time is gonna be maxing out a full size VS. if you plan on having them all on you will have to get creative with the layout. I see about 100' of pipe from pad to the spa, thats gonna be tricky too. If you have an overflow setup you will need to pull pool water too to the spa for that. the main makeup will be the spa drains. Maybe tie a seperate pump just for spa using a skimmer for the pool makeup. then tie the second skimmer and strip for the pool returns. A high flow pump would work best for the water features, if you dont want to go to 3 pumps you could also setup the pool returns and spa like a traditional pool/spa combo and then use a water feature pump to just power the water features. The issues with a water feature pump is its single speed. if you decide you dont want the bubbler on or the waterfall on and just the other the flow is gonna be alot stronger. Pretty complex to automate all of it, you need lots of valves. I like to use 2way valves mainly, I only use a 3way when in between 2 lines, I hate when i see 3ways into 3ways, its a pet peeve.