First..Welcome to RIBnet!
Humbers and RIBcraft are both good hulls, so providing the hulls and tubes are sound then they get a thumbs up from me.
The size of the RIB is largly up to you. 5.85, 6.0 or 6.5? The larger is going to be generaly more seaworthy than the smaller ones, but for a given horspower will be slower and less economical than the smaller ones, so as I said....It depends on your application on what size you go for.
The Honda is a fairly good engine but does suffer from cracked powerheads I believe (around the valves). Is also a little long in the tooth by todays engine choices, is heavy and I think it produces less than the stated 130 horses.
The 90/150 Opti is a cool engine and people on here love em. Check the service history on older ones, but one from say 2003 should give you many problems, just check all the stamps in the book. Don't forget that Optis are 2 stroke oil burners, but can be very economical with fuel.
As for the packages:
The RIBcraft with the Honda should be a fairly good match if a little stern heavy. A sea trial would be needed to see what she handled like. Provided the engine has a full service history, there's no reason why you should have a happy partnership with this one, should be economical too.
6m Humber with Opti 150, is going to be your highest performer as far as top speed and acceleration is concerned. Good match I would say.
The Humber 6.5m with 90 Opti. Good Hull, should safely see you though the rough stuff and get you home. With a 90 on the back! Humm, sell it and get a 150! Would be the best hull if you're looking at offshore cruising, but the lack of performance with the 90 wil mean you're pushing max revs all the time and costing yourself an arm and a leg in the amber go go juice.
I'm sure there'll be other opinions that will just as much confuse you