I made a perry back in March and bottled with carbonation drops in those PET bottles. I was frightened of bottle bombs but actually ended up with terribly undercarbonated perry most dissapointing given how much effort I put into mincing and squeezing the juice from the pears off my own pear tree. I put 1 drop in half and 2 drops in the other half - the 2 drops barely carbonated enough and the 1 drops I shouldn't have even bothered with!
Really depends on where your gravities are at I suppose, but next time for me I'll bulk prime with about 6-7g/litre of regular table sugar (my go to for pales) instead of using the carbonation drops.
Just note, I'm not telling you what to do, instead I'm just adding to your confusion based on my one time experience making a perry! Good luck, let us know what you end up doing and how it turns out.