Upsizing question

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Seattle, WA
This is a variation on a common question, but I still can't seem to find a solid answer.
I am re-piping a house using PEX (expansion) to replace copper pipe that is starting to show signs of problems, and because the whole system has been patched by handymen so many times that the number of shark bites is getting out of control.
The house is supplied by a well with a combination of poly pipe from the well to a short length of galvanized through the slab, then a combo of galvanized and brass to and from the pressure tank. All of that is 1". Then at some point in the past a pretty extensive iron-filter system was put in using 1" PEX with cold-expansion fittings. After all this the pipe then reduces to 3/4 for the hot and cold runs.
It's a 2.75 bath house. All of the baths and the laundry are at the far end of the house from the pressure tank and HWH, about 50 feet away. They are currently fed by a long run of 3/4 copper with 1/2 lines to each fixture. It's all fairly standard (except that there is a pretty excessive number of elbows in the install). Fortunately all of the pipe is pretty easily accessible via the basement.
There are no current complaints about the water flow, except maybe for the laundry sink at the far end of the system. All of the fixtures are updated in the last 10 years and presumably "low-flow". The well pressure tank is a typical 32 gallon tank with a 40/60 psi cutoff switch, if that makes any difference.
So the question is, should that long run of 3/4 copper that supplies the majority of the fixtures in this house be replaced with 3/4 PEX, or upsized to 1" PEX. There would be manifolds with 1/2 to the fixtures either way. I estimate that I will easily eliminate at least five 90-degree bends in both of the the 3/4 copper lines by replacing them with PEX, and many more than that in all the 1/2" lines. I may even be able to do this with no elbows at all, after the filters (unless you count the manifolds).
My concern is that the house has young kids now, but as they turn into teenagers I can see there being a pretty big water demand at certain times in those baths at the far end of the house. On the flip side of that, I don't want to make the wait for hot water unnecessarily long and wasteful by having a long run of oversized pipe.
At one point I also considered replacing the 1" PEX the filter guy used with 1-1/4, but I decided I was creating unnecessary work for myself with little likely benefit, so all my work will start after the filter set-up.
Cost isn't a huge factor, but I'm not especially interested in doing a big central manifold with 23 individual 50-foot runs of 1/2, unless someone can convince me there is a really good reason to do so.
Hey, wait a minute.

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