Hi, and welcome to FT. As I assume you like to have your honeymoon somewhere far away, and fly there in F (or C), you'll need a lot of miles, I guess 200.000+

This won't be reachable within a year or two (When assuming you won't spend 50k$+/year per person) - even including a one-time bonus.

I don't know how much miles you're still missing (I know people who won't say decent unless they get 1 million) but in your case, unless it's something under 40k miles or so (So you would reach it with the bonus+year expenses), go for a card with the maximum signup bonus for yourself and one for your fiancée, return them at the earliest date possible, get new cards and continue. Or do some cards at the same time, with different banks. Just pick those with the maximum of bonus miles when signing up.

About putting both miles into one account, why not keep seperate accounts for yourself and your soon-to-be wife? This would make administration much easier, and booking of awards can be done right from both accounts, without the need/time to shuffle miles around.