[BrianR]

So, i am planning to buy one more light stand and adapter. Instead of strobe lights i will go with speedlight + umbrella setup. Apart from that, i have some old manual flashes.. which I read as very powerful ones. Like you mentioned, they are unsafe on hot shoe. But, are they still unsafe with off-camera connectivity ? like wireless triggers or cords ?

If the trigger voltage is too high, they're still unsafe with a cord. Some of the wireless triggers can handle high voltages of older flashes, some can't. It depends on the trigger.