Cavalier I hope is basically what it is in the most recent UA. I've used it in Boss fights recently, and have a big fight coming up in a month or two with a multiclass Berserker/Cavalier.
Inquisitive is basically Rogue, so outside of free Expertise in certain Intelligence based skills, it will be interesting to see what they get. Perhaps some 1/rest divination abilities.
So Horizon Walker I predict to be a Druid subclass, emphasising Terrain Mastery over wild shaping or spellcasting. Alternatively, Bard, with a Nature focus, or Monk with a Druidic Focus. Or the Boring as fuck Ranger.
The new feats are basically going to be the racial and the skill feats, and maybe a few of the old weapon type focus feats. Can't say I give a toss about the rest.