I think I've had a 9V leak once, I've had others leak internally to the point that the ends were bulging but the outer case gives them an extra line of defense and the smaller internal cells may hold less liquid.
I've been using Eneloops in almost everything for years. I also have some Fujitsu that are supposedly made by the same company, and some of the Japanese Amazon Basics NiMH cells which are also quite good. Some are Chinese so check closely before buying.