In general, a male and a female dog will get along pretty well. Doesn't mean they won't compete for possessions - and your attention - but real fights are unusual, IME.
As to not 'clicking' straight away... I always find this with a new dog, whether it's alongside another or a new only dog. The bond one had with the previous (or other incumbent) dog has developed and evolved over years together. A new one won't be a part of you in the same way for months or years, it can't be. Neither of you know how to read each other yet, what each other's likes and dislikes are, each other's rhythms. In that sense, any new or particularly replacement dog is always a disappointment - it doesn't and can't, yet, replace the previous.
As long as you don't actively dislike the new dog, don't worry, the bond will grow.
You also wonder whether such an 'easy' dog can be as close and valued a companion as the sharper dog.
My first dog, the first that was mine, as an adult, rather than the family pet, was a rescue. He was a one-off and I will never ever forget him, nor will most people who met him. He wasn't an easy dog though. A later dog, of similar type, couldn't have been more different. Loved everybody and everything, relaxed as though on permanent Prozac, but a fun and loving dog. I suppose I never did love Horace in quite the way I loved Moses, but that's not the same thing at all as saying I didn't love him. I loved him to pieces. The most wonderful thing about him was how easy it was to be with him - anywhere, any time, with anyone or anything, you just never needed to worry about what Horace was doing or how Horace would react. To the extent that I realised I would not knowingly choose a dog as difficult as Moses ever again.
So give Lola time.
The only other thing I'd mention is that, if Mojo is already a bit unhappy about other dogs, if he decides that Lola is his bitch, he could become quite aggressive if other male dogs come around her. So if you haven't already had it done, you might want to consider getting him neutered.