>>37532389Use a Wobbuffet, or Crobat with Mean Look to make Lati@s a regular encounter. Also use a Pokemon with Sweet Scent to get them to show up immediately instead of running around in grass.
Fug feels like a hard encounter because it has Rest and it spams it like a cunt. It's a long battle if you aren't equipped to deal with it.
Both are possible to catch with a regular ball but aside from these two there isn't anything more difficult to capture in Emerald, so feel free to use it on whichever one you'd rather not deal with.