The thing thats great about moonshine is that not only is it really great for rams, it's also REALLY great for stopping your forwards momentum very quickly. This way you can easily charge in, but if you feel you will miss your ram you can easily moonshine backwards and avoid a sticky situation.
The most important thing for me about a pyra, is using height advantage. This is the main deciding factor in pyra vs all other ships. You want that gat/mortar to have its good downwards arc, you want your hades artemis to have that downward arc, you can kind of get away without it with hades flak, but its still good tactically to have good downwards arc. This doesn't necessarily mean to use hydro ALL the time, although some good pyra pilots do that (Fiasco total). Personally, I'd rather just rely on a balloon buff to keep me above my enemies. I constrict hydro to escaping, or if I'm trying to get a quick kill on a weak ship and I'm fairly far below them. I just don't like it because it takes my flak/art/mortar engi off his gun and forces him to repair the balloon (and the explosive damage that engi deals most often decides the engagement).
When it comes to hwacha, it's all about the height advantage. It's pretty easy to just stay above a galleon's broadside. Against a spire I'd say aim you're pointy bit at the very top of his balloon and just rush, the hwacha will most definitely hit your underside where there are no components. Hwacha fish is a bit tricky, what you really want to do is catch him off guard and ram his hwacha out of arc (pretty easy against goldfish).
I think the most fun part of flying a pyra is definitely evading. You see another pyra right behind you? Use my patented MysteriousEvade™ maneuver. Hydro up, sparingly, and moonshine full speed backwards. Keep going backwards until you're above and behind them, and then you quickly have the advantage. You'd expect this to only work against pilots who are unexperienced, but I think the sheer novelty of it will surprise even experienced pilots- I've done it multiple times in competitive and it always worked out. First time can be seen here
https://www.youtube.com/watch?v=R-vvPctKeWI#t=3m32s. However, don't do anything else seen there like... say... don't put on phoenix claw while you're being rammed like I did, and don't not shoot at someone when they're right in front of you.... The only reason I had to use that maneuver was because I messed up in the first place.