Question to those who have lots of experience with 4e:
I love tactical combat, but I don't want it to take forever.
You can speed it up, but it requires buy-in from everyone--DM included. Using the Monster Manual 3 stats (which are lower-HP, lower-defense, higher-damage), relying on minions, keeping limits on conditions that excessively complicate matters, etc. On the player side, having prewritten power cards, ALWAYS paying attention even on other players' turns, and tracking turn order and conditional effects as simply and accurately as possible. (A whiteboard is actually very helpful here, along with either colored bands, colored tokens, or magnetic tokens to stick to the white board.)
Been thinking about how to do 4e-ified simple combats too--probably riffing off the Skill Challenge rules--but I haven't done any concrete work yet. If that's of interest, I'll look into it. And on the subject of Skill Challenges, I have some significant advice that...doesn't technically
contradict the SC rules, but rather expands beyond them to make them much more enjoyable than if played precisely by-the-book (which can make them feel REALLY stilted and mechanistic.)
And I generally prefer my D&D simple (Original/Basic/Expert/Classic), with few options and nothing that looks like a "build" or "char-op."
Well, some amount of "options" and "builds" is unavoidable because even the books use the term "build," and part of the tactical combat resides in which choices you make at the (for lack of a better term) "strategic" level. If you want to keep that "strategic" level while cutting down on the chaff, I honestly do suggest the various class guide threads you can find here on ENWorld. Not to be super-duper optimized, but because they cut through ALL the crappy chaff BS and get to the good stuff.
If you dislike it so much that you'd really rather avoid ALL of it, the "Essentials-style" classes are a halfway decent way to cut down on options, but even there there's still going to be feats and
some building of a character (e.g. there are two Cavalier Virtues to choose from). Not all classes
got an Essentials-style writeup though, e.g. there is only the "original" Warlord, an emblematic class.
Given that, how would the following impact a typical campaign?—
• I don't want to fiddle too much with hp totals and damage, but how about simply having everything always cause maximum damage instead of rolling? This seems comparable to halving hp, but easier to deal with.
Well, MM3 stats generally work pretty well for this, but if you want to take it further, this might work. The only problem will be that that's what crits already do (plus some rolled extra dice), so you'll want to make a new rule for crits. Double max damage
could work, but it will make PCs hit really REALLY hard. The other side of this is that fistful-of-small-dice attacks, or simply fistful-of-dice generally, will be a lot more powerful. However, this
will definitely speed up combat, so it's worth considering.
• Are the essentials classes simple enough that an "essentials only" campaign would largely eliminate high-level "power bloat" and option paralysis?
I don't know if they'll really eliminate "power bloat" per se. Several of them end up with a similar number of total powers--it's only really classes like Knight and Slayer that truly excise a lot of stuff. They just don't give you the
choice of what power you take at the strategic level (or a choice between 2 options)--the tactical level remains choice-heavy, IIRC. It sort of depends on what you mean by "power bloat"; is it the pool of options players can choose from when they level up, or the pool of options they can choose while actually in-combat?
• Is there a certain cutoff level beyond which the selection of powers grows especially unwieldy? Level 10? Level 20? (As it stands, I already cap my OD&D campaigns at 10th level for human characters, since the level limits for demi-humans are in the 4th to 8th range. I have no problem at all with a campaign that only goes up to level 10.)
I'd say probably mid-Paragon, so level 14-16 is where things might get too much for your tastes, but it's hard to say for sure. That's when you've hit your maximum total of regular powers and start
replacing lower-level ones, rather than simply adding more. (Utility powers are the only non-At-Will powers you never replace; your pool of those continues to grow, albeit slowly.)