With the advantages and disadvantages you're pretty much spot on. You have a constant stream of fire which is like a flame thrower, and typically these attacks span a wider range. With these techniques though, since you're using constant chakra, you can't use another technique right after, you have to stop the jutsu you're using to attack with another attack.
As for your strategies, I would heavily discourage using any Katon techniques against Suiton techniques. When B-ranks of the superior element can neutralize S-rank of the weaker element, it's not the best choice to use against water. Also, you have a little bit of a misunderstanding to the Katon techniques in this method. With the last set of techniques you gathered a fixed amount of chakra and released it in a glump/burst (the projectiles) this time you channel a fixed amount of chakra into your point of release and then release it in a steady stream until that chakra runs out. The power and will of that fire stream is the same as it would be in the condencsed projectile. For example:
Fire Release: Soaring Flame Bullet=B-rank meaning it costs 20chakra
Fire Release: Fire Breath=B-rank meaning it also costs 20chakra
One's a projectile, and the other is a stream of flames, however you're focusing the same amount of chakra in both technique and exhaling flames with the same amount of fire and power. If these two techniques where to clash with one another, it would be a stalemate. If you wanted to continue using Fire Breath, you would have to focus more chakra and then do it once again. The matter of time it would take to do that is arguable. It wouldn't overpower a water technique by simply saying, you add more chakra in the technique to sustain it, that would just be you, re-using your technique the in your next turn. However, you could do this
Fire Release: Fire Breath and should your opponent use a stronger technique, you could simply say you add more chakra to it and then say you use Fire Release: Great Fire Destruction. Both techniques are essentially the same only one has more chakra and is bigger. However the difference between what I said above and just said now is this: In the individual techniques you're focusing on a fixed amount of chakra and releasing that chakra in a stream, so saying you add more chakra to that but still saying it's the same technique would only mean you focus that same fixed amout of chakra again to use that technique a second time. To say you add more chakra as in, a larger amount and release it as a stream would be what I just did with the example of Fire Breath to Great Destruction. Does that make sense to you?
Other than that, you have everything else nailed. Do you have any questions?