Second question: how do synchro blades compare to dance blades?
A lot of people think they are intermediate between freestyle and dance.
The only Synchro blades I've used are the Jackson Ultima blades, specifically Jackson Ultima Matrix 1 Synchro runners. They had toe picks intermediate in length and aggressiveness between Ultima Matrix I Supreme and Ultima Matrix I Dance. But they had tails that were shorter than the tails of both the Dance and Supreme runners - perhaps Ultima thought that Synchro offers more chances for people to step on other skaters' blades, so needs extra short blades?
But Jackson Ultima Matrix 1 Synchro runners are now out of date, because Ultima has dropped both the Matrix I line, and the "Synchro" line. (Jackson Ultima blades
now include another Synchro model called "Finesse".)
In addition, the Supreme model is a high end competition model - I can't say how they compare to lower end Ultima freestyle blades. I would assume their toe picks are more aggressive than lower end freestyle blades too.
I admit that isn't very useful, since it is all out of date... Sorry.
I honestly don't think losing your balance to the rear is much of a problem on the Dance or Synchro blades I've tried - unless, perhaps, you are doing a difficult backwards landing jump, or you are a beginner. But I can't speak for everyone.
It's a shame that, with the end of Matrix I, there are no easily interchangeable blade runners in the figure skating world, so you could easily switch between inexpensive blade runners and styles. (Several convenient interchangeable runner systems exist in the hockey world.)