PEX Tubing for a remodel

So right now I'm into a remodel of the ranch house. A lot of walls are down to studs. Prior to closing in these walls, my uncle talked me into re-doing the copper plumbing with PEX. I decided to run all of this in the attic and drop down through the top plates.

Any suggestions? Do I install a manifold and run to the outlets? Or just run it all together?

1/2" or 3/4"?

Also, I will be remodeling both bathrooms and the kitchen is currently down to sheetrock and bare floors.

Thank you in advance.

'Can't help 'cept to say, your uncle is a wise man. We're chasing leaks in the copper in this 2003-built house.

I would put in a dedicated return loop with 3/4” on the hot side so you can run a circulation pump efficiently. Pending on the fixture count, you can get away away with a standard drop design.

manifold if you want zones you can shut down, drop style if not.
run one size larger than the drops to help hold pressure if multiple fixtures are in use, bigger is better to maintain pressure.
and what topwater said unless you install an on demand hot water. we run renaii out here (2 @ 9.5gpm ea.) and they are way better than a tank style wh. and are wall mounted outside so no special venting needed.

This, I wish the house we live in now had this, so if/when there is a leak you don't have to shut down the entire house to isolate the leak.

I also second this.
I installed a small one to shut off the 2nd floor bathrooms in the event there's a leak.

PEX is very easy to install.
I repiped the 2nd floor to my house entirely myself (Galvanized to PEX) on a Saturday.
Parts were about $300. And I saved myself about $8,000 in labor costs.