Answer: The general answer is "yes," both the park models and regular RVs can (and should) be treated the same with regard to landlord-tenant laws. However, there are certain regulations that you must follow to ensure that the park models fully qualify as "recreational vehicles" as defined by Oregon law.
First and foremost, a "recreational vehicle" is defined by statute (ORS 446.003 (33)) as a vehicle "with or without motive power that is designed for human occupancy and to be used temporarily for recreational, seasonal or emergency purposes" and as further defined by administrative rule. "Recreational vehicle" is then defined in various rules as (1) being identified as an RV by the manufacturer, and (2) not exceeding 400 square feet in the setup mode, including all tip-outs, slide-outs, expandable rooms, and other horizontal projections.
However, this does not mean that park models cannot be equipped with various accessory structures like decks, steps, porches, roof overhangs and other similar construction. The guiding rule is that these external structures cannot be supported by the RV itself and cannot be enclosed with walls, glass or other solid materials if that would exceed the maximum allowed gross floor area of the RV.
While there are other construction exceptions as well (basements, lofts, certain bay windows, freestanding cabanas, etc.), you should consult with a knowledgeable expert to carefully comply with these regulations. The primary Oregon Administrative Rules can be found at OAR 918-525 and 918-530, which are administered by the Oregon Department of Consumer and Business Services, Building Codes Division.
Assuming you meet the park model regulations, you can use the same rental agreement that you use with regular RV tenants. In many cases, MHCO Form 80 (RV Space Rental Agreement) will work just fine. In other cases, you may want to use a form specifically designed for your park - just make sure that it contains all of the required information, such as how accessory buildings and structures will be dealt with at the end of the tenancy.
In any event, an RV tenancy (unlike a manufactured home tenancy) can be terminated with a no-cause notice if the tenancy is month to month. If the tenant has been in the park less than a year, the no-cause notice period can be 30 days. After the first year of tenancy, the notice period must be at least 60 days. While you would certainly hope not to need to evict a park model tenant, since they technically live in "recreational vehicles," the law gives you that option as a landlord.