To invest in a toddler bed at this point means 2 things: short-term use & yet another transition for your little one, most likely in less than a year's time. The only time I would ever use one is if it was a crib that converted to one & then converted to a twin bed. But otherwise, just move him to a twin bed.
We moved our first boy at 18 mths, only because he hated the crib. Slept great in the twin! I know of kids who were moved at 12 mths simply because the crib was needed again.
I bought the longest bedrail I could find online, then put the rocker backed up against the end of the bed, so he was still essentially protected as in a crib. It doesn't matter if you take the rail down in 6 mths or 3 yrs from then, they will have episodes of falling out simply because they have to get used to it not being there. "Earlier is better" when it comes to transitions like that because they don't realize the freedom they have at a younger age & typically won't "fight it". We left the crib up for about a week, expecting him to fight the transition. It was so easy I couldn't believe it!