Last time I checked, only the stock 152 and the TBM couldn't be removed via the Content Manager. But the issue you may run into is shared components that aren't in a "common" folder as you'd expect. I have the mid-grade "Deluxe" package, and all the aircraft I have in my Official folder only add up to a little over 15 GB. The only thing I've deleted were the MSFS liveries and those hideous black liveries - and those were deleted via the Content Manager. Thankfully, they've never been put back by any updates. If you don't want to see them, the best option is to just disable them from the menu as mentioned above. You can also remove them from the ramp by changing isAirTraffic = 1 to zero.