Many joint manipulation can be done full-speed and full-range (or nearly so, at least) with a partner. You just need a good partner who can recognize the lock early and drop out of it, rather than resist, so you can complete the movement without damaging them.Depending on your art, it cannot be done, correctly, with a partner. You cannot practice joint manipulation full speed with a partner, as pretty soon you will have now partners left. Similarly you cannot perform many throws as truly intended as they will similarly injure you partner. The only time you can practice these things correctly, or at full speed/power is on your own.
With throws, there's a trade-off on both sides. With a partner, it's best to not go full-speed often. Without that partner, you don't have their mass as ballast for your movement, so the movement must be altered somewhat.