How many drive wheels are too many for O27 curves?
It will depend on how many of the drive wheels have flanges.
With x-6-x, x-8-x etc drive wheel arrangements, the inner drive wheels are usually what are called Blind Drivers.
They lack a flange, which keeps the inner drive wheels from binding while going around a tight curve.
You will want to go with larger curves with larger locomotives, but with the Hudson type locomotive, you can run it on the O27 curves. Just make sure you run the locomotive pointed in both directions to equalize track and wheel wear.

Happy Rails!
Dave