I absolutely love Halo 5's warthog and think it's by far the best version of it ever !! Any chance I get to use one I'm in. Sounds cool, drives amazing goes exactly where I want it to go. I think you just have to keep in mind that the terrain is actually bumpy and has edges like the world would have and it rips pretty hard so you can't just hold the gas like old slow warthogs. You actually have to drive this one. The gun gooses are a bit bumpy for sure, but again that's just how they would interact with the terrain. Once you get the feel for them they can be quite the handy little weapon.
I did struggle with the tank for the longest time, I actually created a forge map so I could get better at it. I still struggle at times with it, but I think it's generally how I hold the controller. I have big hands and these new age controllers are a bit too small and cramped so I tend to push the stick to the side rather than straight which leads the tank to going in wonky directions. haha. Other than that I love the vehicles in H5. The demo clip from Halo:I left me thinking that the new warthog won't be as much fun to drive though. We shall see.
Just load a map into forge and then spawn in all the vehicles and cruise around. You'll get it in no time. https://www.halowaypoint.com/en-ca/games/halo-5-guardians/xbox-one/map-variants?lastModifiedFilter=Everything&sortOrder=BookmarkCount&page=1&gamertag=ooSnip3r#ugc_halo-5-guardians_xbox-one_mapvariant_ooSnip3r_10cf63a2-3921-4dba-925a-b8e972ada81a Lots of different vehicles to use in this map already.