Anytime I've experienced tearout with my DW735, I just take a smaller bite and it clears up. You can plane against the grain with the stock knives, provided they're sharp, if you're not trying to take off too much. My only complaints with it are the noise and knives don't last long. For me, they never last long enough to get close to dull. They get chips and leave tracks like crazy. But you can shift them and flip them, so you're not constantly replacing them.

I wouldn't mess with a helical head. It doesn't add anything in practice and risks overheating the motor.

Also, I don't know what benefit a smaller planer would add for you. I feel like snipe is more of an issue with that planer if you don't use sacrificial boards. And at that point, might as well use the big one and not mess with the added space it takes up or wasted money and time spent changing a second set of knives.