Will be very interesting to see how the RB-situation pans out. From what I've seen (not a lot) so far, Emerson is not typically "Brazilian" going forward, but very solid defensively. He's also rather tall and physically strong, which might help defending standards.
Dest is still very young, but after showing promising signs early on I'm not impressed by anything he showed in 2021. For a player whose forte is going forward, he offered very little and was toothless considering Koeman very often played him as a wingback, being freed from doing as much defensively as he'd have as a right back.
On paper Alba and Emerson might be the more balanced full-back - pair. However, I don't think Dest has a disadvantage because Koeman prefers physical players. Dest was pretty much Koeman's one and only signing last summer, one the coach was demanding strongly.