I've seen videos from TNT Amusements where they literally are just flipping breakers to turn things on and off. I have both of my machines on a surge strip that has a "smart" plug on the wall side. So I just say "Computer, Pinball On" and they cut on or off. I've even seen someone fast cycle a Williams Firepower 4-7 times(not sure why they did it, but on and off super fast) and it was fine. I wouldn't really feel comfortable doing this on modern machines though.

I'm sure even newer pinball machines have something to protect them from damage. I've never turned a newer one on or off, but I assume you just use the switch. If it required a shutdown from the menu, I'd say it's not a good idea to just shut it off.

Another thing to note is that modern computers can be hard shut down without problems.(Same with flash drives, just make sure you aren't transferring something or accessing the data when you do it).
It's not like it was back in the day. Modern hardware has made it much safer to just shut off.
You shouldn't do that all the time, but if something freezes or locks up...you don't really have a choice

Love those things. I bought a 5 pack with 2 remotes for $35 years ago and use those with my Christmas trees(wife demands 3, 7'-9' trees in the house). They work really well and the remote works over great distances.