Both are simple, minimally-mechanical thrust engines with little or no moving parts.
Is it possible to have the same motor work as a pulsejet at low speeds and transform to ramjet at high speeds?
Sure. Well, kinda. Well… No - You’d need to provide shutters for the ramjet inlet, and arrange to have a variable internal configuration, probably by moving plates, and a host of other adaptations. But why bother? A pulsejet is supremely unlikely to be an efficient or reasonable means for getting a ramjet up to speed. IIRC, pulsejets cease to operate well below minimum ramjet speed, so there’d be no purpose to such a hybrid.
Not mention that most hybrids are compromises that do nothing particularly well.