1. Yes. She gets twice the % if the gift is her favorite. One tip with gifts is to focus on 4 girls with different preferred gifts at a time.

To illustrate the first answer: X girl's favorite gift is cake. If you gave her a large cake (+3% base), she'll get +6% instead of the +3% from a single gift, maximizing it because it's her favorite. If you give her any other large present (toy, book, or jewel), she'll only get the base +3% and that's not efficient.

2. Evolution doubles the HP/ATK/DEF stat bonus depending on what her current % is. The % itself doesn't change. For example, if a girl is at 98% affection status upon evolving, she stays at 98% after evolution, but the HP/ATK/DEF stat bonus that goes with 98% affection status will be doubled. The final stat bonuses will be the same ultimately.

I though number 2 was disproven?

The max affection bonus remains the same whether you evolve your knight at 0% affection or at 100% affection.
It gets doubled on evolution, yes, but it gets double stat gains after evolution as well, which in the end makes no difference when the evolution occurs.

Re-reading it I think that's what was being said I just misread it - sorry was late in the evening got me confussed

Actually, even if it change nothing at 100% affection, it's still better to evolve a girl with 100% affection than with 0%. When you evolve a girl, she is back to lvl 1 and get lower stats than her lvl50/60 pre-evolved form. But if she is 100% affection when she evolves, the double affection bonus compensate the stats loss and she will have almost the same stats than her lvlmax non evolved form. It really matters u til you get enough good evolved girls to make solid squads.

Ok,
Thanks for the awnswers.
It'll be just a matter of luck with Manyus and Dragons then (not receiving only lvl 1 dragons after doing the 80 stamina map would help a lot, but anyway haha)