You will have to ask these people if they are willing and able to write an outstanding LOR for you. If a person hesitates for any reason, do not acquire a letter from them. The other professors that you know will be able to attest to your qualities, which will most likely lead to a better LOR. In your particular situation, I would consider the quality of the letter first, and credentials of the references second (as long as they are a professor, former employer from an OT related setting, or OT, you should be good)
Personally, I sought LORs from people who are advanced in their profession (have 20+ years of experience in their career and hold key positions or have advanced certification/specialization). For the most part, I planned this way ahead of time, which is what you want to do for an LOR. Sometimes unexpected things occur too, which is why you should also establish strong relations with many people.
IMO, acquiring a LOR from an OT is a must, since a lot of schools seem to prefer this, and it would add a lot of weight to your application. Concerning professors, I'd say that a pre-health professor that you took anatomy and physiology from is ideal.