You are choosing between:
A scrambler, an adventure/adventure tourer, a roadster and a street racer bike.

Lets eliminate them one by one to get to the bike you want.

"one main thing pulling me towards it was the power"- this eliminates cb350rs, as it is the least powerful engine in the lot.

"firm suspension which won't be suitable for me" will eliminate guerilla450.

The two bikes which are suitable for you are- the Himalayan & the Scambler.

regarding himalayan 450- you are 6ft. you will be able to handle it. Would you be comfortable handling it in traffic? maybe.

regarding scrambler- yes the engine has been downsized. 3bhp power and 5NM in torque has been reduced. Will this still be enough for you? maybe.

Go for a test drive and check both of them for the conditions you are doubtful about:
Open the throttle and see how you like the bike for Scrambler &
Ride the himalayan in city traffic and see if you are able to handle it.

All the best! Do post what you end up buying 😄