The reason I use an inverter in my truck is because modern vehicles have a lot of electronics and circuit boards and computers that run everything from motor to transmission to you-name-it. Sometimes when you plug in devices it can cause interference with the vehicle computers. Yes, this has happened and the fix was to unplug the toys. The real solution is to use an inverter!
The inverter separates the vehicle electronics from the devices you are charging, no more interference.
The other benefit, as mentioned, is you get a cleaner power source, especially if you use a pure sine wave inverter vs a modified one.
For chargers and bricks you can use a modified sine wave inverter, but the pure are so cheap that I would never ever again use a modified sine wave. Not everything can be plugged into a modified sine wave, these things will fry quickly.
A 300 watt inverter is plenty for what you are doing, is small too, but use 8 gauge wire and connect as directly to the battery as possible, 10g ok, but if you have 8 is good. I plug into a DC outlet and that powers 5 usb outlets, and run all my stuff off those outlets. I have not yet run the direct 8 gauge wire....
Yes, seems nonsense to go from DC to AC back to DC but this truly is the best solution.
I also charge my 18 volt tool batteries off this inverter, charger plugs into 120 outlets, it is the only way I have charged them for the past year. Is nice when you use tools for work and just charge them while you drive to next job; batteries never leave the truck.
A pure sine wave inverter, even the cheap ones, have very clean waves, far superior to what comes off the power lines.
If you have sensitive devices then using an inverter is just smart.
I have the exact same 300 watt inverter in my camper too. It runs a small TV and charge laptop, never needed it for anything else. The TV is 18 volts and I want to get a step-up transformer but just easier to use the inverter. Always keep an eye out for 12 volt tvs. TVs will plug into 120 wall outlet, but all run on DC power, the change happens inside the TV, but you can open the tv and bypass the transformer if you have the right voltage. 12v tv will run on 13.5 easy enough.