I have not used the latest crop of power conditioners but in the time period I was playing with them you could hear their effect; I don’t know if, given the state of dirty power in a particular locality, it is worth the trade-off.
I’m currently using whole house surge, and a surge board on the secondary side of the big (10kVa) isolation transformer. No other black boxes.
On less critical stuff, I have, in addition to the whole house, point of use. I probably have at least 3 units or more offline, including a 240 v. step down, a big power conditioner from Richard Gray that ran the video system (not sure it is sonically up for high end audio) and Furman, etc.
I think the value of these things is dependent both on the quality of incoming power as well as the system in which it is utilized.
In terms of protection, to me (thankfully have not experienced it) but a direct strike, all bets are off (unless unplugged).