After plumbing quotes around $4000 to add a full bath we've considered doing the work ourselves. Our house currently has copper, but we would like to use pex to supply shower, sink, and toilet.

My questions refer to running pex to the different areas.
Do I need to use a PEX manifold added onto hot and cold water lines and then PEX to each fixture?

Where is the best place to make this transition to PEX?

If using a manifold do I need to be mindful of the sizes of PEX to each fixture and the order in which they are run?

Is PEX typically ran to a copper stub out near each fixture so that shutoff vavles can be used and the PEX is not exposed (especially on a pedestal sink or toilet)?