Lemmy federates with Kbin, so yeah, it can access the same content for sure. I just mean that, given the length of time Lemmy has been around, there was an existing community of regulars who were already posting heavily on Lemmy servers by the time Kbin started taking off. But yeah, thanks to federation, it doesn’t really matter where the content is originally shared as long as Lemmy and Kbin can both access it.
Tusky is best for those who are newer to Mastodon. Visually it’s very clean, straightforward to use, and largely free of bugs (it helps to have been around for so many years).
For users more familiar with Mastodon, I’d go with Fedilab. Despite a few bugs, it’s the most customizable option, with so many features you can tweak to your own tastes.