The last time I flew, I just put an iPad, the DI, tuner, headphone amp for my IEMs, a set of bass strings, set-up tools for a bass that was supplied for me when I arrived, 230v to 120v adapters, and phone chargers into a backpack. I kept it as carry-on, except now I have a 55-lb backpack!
I swear, the only thing that caught TSA's eye was the lineman pliers I had in the backpack. I couldn't keep them in a carry-on bag. Which I understood. I could get one at the destination. And they looked over my meds and CPAP machine in my carry-on suitcase, but no more than a quick lookover.
And this was going to and coming back from Prague, Czech Republic.
I have a feeling that what gets whose attention on any given day varies wildly, but I had no trouble in both directions. But DAMN that backpack!