Can i use intervalometer to engage continuous shooting (setting continuous with speed ~5fps on camera instead of bulb) for 20 seconds and delay/timer of few minutes ? (with sony a6000)

Yes, you can (assuming you mean an external intervalometer hooked to the camera's wired cable release port). When the cable release completes the "full press" circuit via the camera's cable release port, it has the exact same effect as pressing the camera's actual shutter button fully (other than the camera motion that might be introduced by touching the camera).

If the camera is set to 'Bulb' the shutter will stay open for the length the cable release maintains the completed "Full Press" circuit.

If the camera is set to a specific shutter speed (more accurately called a shutter time or time value), then when the "full press" circuit is completed by the cable release the camera will fire the shutter for the set shutter time.

If the cable release maintains the "full press" circuit for several seconds continuously the same thing will happen as if you pressed the camera's shutter button for the same number of seconds.

If the camera is set to "single shot" one photo would be taken.

If the camera were set to "continuous shooting" as many shots as would be taken while holding down the camera's shutter button for the same number of seconds would be taken when the cable release maintains the "full press" circuit.

For more on just how simple and near universal, other than the shape of the connector, the connections between cameras and wired cable releases (with or without intervalometers) are please see this answer to Is there a good remote timer compatible with most Nikon and Canon (and Pentax and Sony) cameras?