No, and - in most cases - no.
The Middle Housing Project in no way relaxes the statewide uniform building code. That said, the law requires the Oregon Department of Consumer and Business Services (DCBS) Building Codes Division, which manages amendments to the building code, to create an alternate approval pathway for internal conversions of houses into two or more dwellings. This would make it easier for a house to be converted into a duplex or triplex. Consult the Oregon Building Codes Division directly with questions on this specific topic.
Regarding street improvements, Woodburn Development Ordinance (WDO) Section 3.01.01D has a limited exemption for building a house on a lot in a long-established neighborhood, namely exemption from street widening, sidewalk, and a landscape or planter strip for street trees. It appears to City staff that state law requires that if the City continues to allow exemptions, that it administer them equitably for both houses and middle housing types. The City might instead eliminate the exemption.
The City is forming a technical advisory group (TAG) as the main body advising the City staff and officials on what amended regulations should be. Contact the Associate Planner if you're interested in joining the TAG to influence the rules the City Council might review and adopt.