Cactus KF36 Portrait Flash Combo

[Class A]

What do you think of this Cactus KF36 Portrait Flash Combo?

1. Are the flashes (Vivitar 285HV clone?!) a good buy or should I rather search on the used market?
2. Are the flash diffusers useful?
3. Is the flash bracket useful to be used with the camera to bring the flash to the side of the camera?

I'm looking for a small set I could use for product and portrait photography.

I think the Cactus V4 system will be sufficient (not intending to enter professional wedding photography).

Should I go for flashes which swivel if I buy new (the ones included don't)? I know that the Pentax 360 and 540 flashes are nice but they are rather expensive.

Are the diffusers useful or do you need flash umbrellas anyhow?

Any advice would be greatly appreciated.

P.S.: I already have a Vivitar 2500 but it cannot be manually controlled apart from two thyristor settings.