I believe it was the Yachting Monthly that published an extensive material on this issue last November or October. You can get a copy in your library or ask them for a copy via e-mail. It is worth it as they made real life tests and they went thru a good choice of props.
- yes 3 blade
fixed is better that the folding or feathering, except for some expensive and good designs of the folding that do deliver,
- yes it drags a lot,
- freewheeling is less drag than locking, but not all transmissions are designed to be left freewheeling,
Note - if your 3 blade fixed was not the perfect match then you might match up or exceede it with a well matched folding / feathering!