Keep in mind the 4" DX3 is a big rocket. The weight on the website is likely the bag-o-parts weight and will increase with boutique and paint and so on. Especially if you go dual deploy. If you are not careful you could end up with a rocket that will only fly on the bigger L1 motors and L2 motors.
Heavier rockets need more kick to get enough speed before leaving the rail, or longer rails. And that means bigger motors and often more altitude, not always, but often.
38mm is great for L1 rockets. Gives you a large range of motors to fly on and you can adapt down to 29mm if you want. I'm all for building bigger and adapting down, but I never adapt down. 54mm gets 54mm and so on. Build your L1 rocket to fly....L1 motors. Build another rocket to get L2.
Dual deploy is not difficult at all. And it's a good skill to have; crucial for flying high. JLCR is a viable option in the shorter rockets.
I vote Goblin. Build it efficiently and it'll do the job, no need to build a tank. 4lbs is a good target weight for L1. The Goblin will be draggy too, which will keep it lower. The MMAS isn't complicated. You build a rocket with a large MMT and build an adapter to fit in it. If someone finds it too complicated, maybe said someone isn't quite ready for HPR. Not picking on your Dr Wogz.
The Goblin's main tube is 54mm...so when you get ready, you can take out the smaller MMT assembly and slap in a 54mm 1 or 2 grain, not for a L2 cert flight...just when and if you get ready for it. You'll love it.
Their is absolutely nothing wrong with paper rockets with 54mm motors. My Tyrannosaur went to 6500' on a K600, no problem.
The Zephyr would be okay too, I'm just familiar with LOC. PML Tethys wouldn't be a bad choice, the Quantum tube, not phenolic, would be sufficient for L1. I personally love the stuff. It would be a bit on the heavy side. The Bumblebee or Mystic would be better.
Ultimately, do it how you want to. If you want a rocket that has to fly on the I600 to get your L1, do it. I did electronic apogee with motor backup, 2.6" scratch fiberglass at 64oz. Fun, fun.
Have fun!