Between the fixture and the wye fitting, there should be a vent.
If the fixtures are vented that way, then the order makes no difference.
We are working on a new modular home on a basement. There will be a horizontal branch line servicing the water closet, vanity, shower, & washer. All of the fixtures are individually vented. Does it matter where the water closet enters the branch line (i.e. upstream or downstream of other fixtures)?
What about the washer?
WHERE the fixtures go is immaterial. Whether you have the proper vents on them IS important regardless of how you have them arranged.