At the end of the day, a smaller adult tends to be stronger naturally than a taller adult because they have shorter levers. This isn't always the case but take a million people 5ft tall and a million people 6ft tall and you will find on average the 5ft tall people are stronger.
It depends. There's a balance of competing factors between physiological strength (muscle length, cross sectional area, volume), neurological strength (recruitment), and mechanical strength (the muscle's force angle on the lever that you mentioned).
The cross section of a muscle dictates its absolute strength, and this scales with height by a power of two. The volume of the muscle, and thus its weight scales with height by a power of three. So if you double someones height you multiply the strength of their muscle by four, but you also multiply their weight by eight.
Research in power lifters has shown muscle strength and height are related by a common factor, but that muscle strength approaches a maximum at about a height of 183cm for men, and 175cm for women. At this point other factors start to out weigh the cross-sectional advantage.
So if you want someone to curl free weights, you might find the taller tend to be stronger than the shorter. But if you want people to do pull ups you'll find the shorter to appear stronger.
