Loki330: Pretty self explanatory...
I don't know all the answers to your questions. I don't know if anyone here does; you may be the first to find out.
Here's what I do know.
1) If you choose a background which starts you off with a boost to either BE or CH (or both), you will be able to increase that stat above 20. The reverse is also true; if you make yourself ugly and/or boorish on purpose, you will never be able to max out those stats with that build.
2) High enough BE negates the racism you'd otherwise receive from being a Half-Orc or a Half-Ogre; nobody ever gives you grief about it. Depending on your roleplaying goals, this could be a benefit or a disadvantage.
3) Beauty affects initial reactions and purchase prices (including at the train stations, believe it or not). If the initial reaction is negative (below 0) shopkeepers may refuse service and certain other NPCs may attack on sight.
4) Haggle (which is tied to WP) affects selling prices.
5) You can never sell for better than cost, or buy for better than 1% above cost, no matter how high your BE stat goes. Exception: if you sell an unidentified magical item (mostly daggers, though there are exceptions) you may get far better than cost than if you'd bothered to have it identified (or done so yourself).
6) The spell
Purity of Water gives a +4 boost to BE while it's active. It stacks, so most PCs can start out with a +8 boost right off the bat.
7) The elegant or Sunday's Best dress (for women) or smoking jacket (for men) gives a +20 boost to reaction while worn. This is also the approximate equivalent to adding 4 to BE, even though that stat doesn't change.
8) The only Large smoking jacket in the game is worn by Gilbert Bates's manservant. It's possible to pickpocket it off of him, possibly using a Fate point to guarantee success.
9) Completing Arbaleh's quest at the very beginning of the game gives a permanent +5 boost to reaction. This is also about the same as adding +1 to BE, even though (again) the stat itself doesn't change.
10) Getting BE to 20 or higher increases NPC reactions by +100%, +10% more for each point above 20.
11) Getting CH to 20 or higher means that you can recruit any follower (even those who wouldn't normally join due to your alignment) and followers will never abandon you, regardless of how you behave.
12) Persuasion is tied to CH. Most persuasion-related quests require one rank in the skill. (One also requires good IN, to call up the best answers; if you know it well enough to do it fast enough, a potion of IN will do the trick.) A few require two or three; only the master quest (and a potential endgame quest) require you to have all five.
13) The Haggle Master is located in Tarant, in the bar. Even if you choose not to complete training, he has a ring (which again, you can pickpocket) which gives a huge +3 boost to both BE and CH, as well as a boost to both Persuasion and Haggle.
14) You can get a permanent +1 boost to BE by helping the priestess in Stillwater (which you will need to do anyway, if you plan on following the elaborate Gods Quest side quest; see below).
15) You can get a permanent +1 boost to CH by helping the Tarant fortune teller take revenge upon her rival. The secret (
MINOR SPOILER) is to a) find out about the stolen painting, b) introduce yourself to her after you've been given that quest, c) complete her crystal ball quest, d) complete the other quest WITHOUT returning to her for the clue she promises you, and then e) getting the CH boost as a reward instead, because she feels obligated to give you something.
16) If you pursue the Gods Quest, you can get a "temporary" +1 boost to BE twice during it: once early on, and once near the end. (They're temporary, because you'll lose them as you pursue the quest further.) The Gods Quest is convoluted and has to be followed exactly; I recommend a walkthrough if you plan to go that route.
As for the rest of it, play through and tell us what you discover.