New Game++ unlocks after you complete the base campaign and New Game+. It is a significant step up in difficulty in terms of bullets and screen congestion, but none of the tactics really change. The key to reducing the difficulty is a maxed out ship. After 2 full playthroughs your ship should be mostly maxed making New Game++ an much easier experience. I wouldn't consider myself more than an average SHMUP player and I only had to repeat a few levels with a maxed ship. Good Luck!
If you are having some difficulty here are some helpful TIPS:
- Make sure you have points in HP for your ship. The game is very generous with HP drops and with a maxed 250 HP ship you will find that you really don't have to be great at dodging a lot of fire, just be a meat shield basically.
- Don't underestimate the power of equipping bombs as your special for bosses. They are slow but they rip though bosses HP on any difficulty. Also, if you use your special right as it maxes the gauge you get a bonus 5th bomb.
- Don't forget to boost thru congested areas. I never used the ability in the first 2 playthroughs but found it very helpful to basically skip dense rooms by boosting past them.