My recommendation is to switch from a crib to a twin sized bed, bypass the the toddler bed and go straight to twin or full, depending on what your plan is for the next few years. My son transitioned to a twin at 3 years, my daughter to a full at 2 years, 8 months. Both were low to the ground, and both did fall out a couple of times, but we put some pillows on the floor so they had a soft landing. They never did it more than a handful of times.
As far as the freedom, we just kept going in and placing them back into their beds. The baby monitors would alert us that they were up. Both were so excited to have big kid beds. We told them that if they couldn't sleep in their big kids beds, then we would have to put their cribs back in their rooms. Neither wanted that. Eventually they stopped fighting, it was just a point of being consistent. We did need to take the toys out of both of their bedrooms and put them into a playroom, as they would get out of bed and play with their toys. That eliminated that problem, and over time we were able to slowly move them back in.
Good Luck!