I've been taking a close look at the alchemical bombs in Pathfinder Second Edition. It's nice to have so many neat tools for alchemists, and that they cover so many types of damage, but I've seen some commonalities that allow you to play with the numbers and create more fun toys that go boom.

First, let's lay out what the rules already give, broken down into four categories: damage the bomb does, persistent (that is, ongoing) damage the bomb does, splash damage the bomb does, and other effects the bomb imparts.

All these bombs have higher level versions, but the higher level versions are very same-y: they all have the same levels, they increase bonuses to hit with the bombs at the same rate, the increase dice of damage (and, usually, points of splash damage) at the same rate. So when we play with the basics, we already know what to do at higher levels.

From the Core Rulebook
Acid Flask (acid damage): Damage 1, Persistent 1d6, Splash 1, Effects none
Alchemist's Fire (fire damage): Damage 1d8, Persistent 1, Splash 1, Effects none
Bottled Lightning (electricity damage): Damage 1d6, Persistent 0, Splash 1, Effects flat-footed for 1 round
Frost Vial (cold damage): Damage 1d6, Persistent 0, Splash 1, Effects Speed penalty for 1 round
Thunderstone (sonic damage): Damage 1d4, Persistent 0, Splash 1, Effects deafened for 1 round

From the Advanced Player's Guide
Blight Bomb (poison damage): Damage 1d6, Persistent 1d4, Splash 1, Effects none
Crystal Shards (piercing damage): Damage 1d4, Persistent 0, Splash 3, Effects creates crystals caltrops and handholds
Dread Ampoule (mental damage): Damage 1d6, Persistent 0, Splash 1, Effects frightened (a very powerful condition!)
Ghost Charge (positive damage): Damage 1d8, Persistent 0, Splash 1, Effects enfeebled

There are a few things we can see here:
* Some damage types are higher because they're generally less effective: fire and positive (which only hurts undead).
* Some damage types are lower because they're generally more effective: sonic and piercing.
* Splash damage is always very low unless the bomb's "special thing" is to do splash damage (as seems to be the case with crystal shards).
* Persistent damage is roughly equivalent to regular damage, which is something I've noticed is roughly the case throughout the game in other areas (like monster damage or spell damage). 
* Bombs rarely have very powerful effects, unless that's their "special thing," as with the dread ampoule; lots of creatures don't take mental damage, so having a weaker type of damage means the effect can be stronger.
* Crystal Shards breaks the level structure a little bit, and the numbers analysis above assumes a "base version" of that bomb that the rules don't actually provide (but could!).

With these observations as benchmarks, we can mix-and-match to create bombs of our own, which I'll do next time!