If you are trying to keep cost down and still have convenience, I would also look to book a value onsite. These days it is hard to do parks without early entry--even with
Lightning Lane. Value will get you that extra time and reliable, frequent bus transportation (or even Skyliner). Also depending on when you're going, there may be room discounts, and no resort/parking fees either.
I have stayed offsite at various places (Marriott Village properties, Hilton LBV, Vistana Resort), but always with a car, so can't comment on the transportation. But it is also easy to Uber/Lyft to parks, it's not that pricey and honestly it's worth it for the convenience. Offsite properties will not run buses with the same frequency.