Played and completed this game a couple of years after completing the original Kingdom Rush.
To the extent of my recollection, it pretty much feels like more of the same, but with some improvements.
However, the original formula was entertaining enough that it hasn't grown old yet (though I might wait a couple more years before playing the next iteration). In a way, it is almost like replaying the original game, but different and slightly improved so if you ever felt like revisiting the experience of the original, but also desire the surprises of a different game, you are in luck.
In terms of progression, I'm sure there are many mixes that I haven't yet tried, but it did feel like the choices heroes and your level up abilities are far from equal. The first couple of stages are a breeze either way, but if you struggle a lot after that, you'll definitely want to experiment there. Thankfully, you can reset your skills, though you'll have no suck luck with your heroes as they level up separately (so if you pick the wrong hero and need to switch, you'll probably need to level up the replacement, though 2-3 battles should do the trick).
Otherwise, the game requires thought, but is not super deep. You'll need to visualize the routes of enemy movements and plan tower placement accordingly, sometimes adjust troop placements during battles, use your meteors and mercs judiciously, but once you figure that out, you can pretty much ace the game without too many retries (not saying you'll ace all the maps on the first try as most maps will throw curve balls at you that you'll need to adjust for on your next attempt, but if you learn well from your failures, you should ace almost all maps within 3-4 tries). On normal, I never had to scrap and change towers mid-game or think too deeply about the synergy of different types of towers.
Also, once you finish the main game, I highly recommend going through the mini-campaigns. While shorter, I think they are even better.