They won't complain about magic items per level, because I'll give them what the book expects. Just like they didn't complain when I gave them proper gold/level in 3e.
Huh? I thought 5e didn't
have expectations about money or magic.
when I'm setting encounters they are meant to succeed at, I consider what they can reasonably handle and I build towards what I want the outcome to be: easy success, challenging success, or pyrrhic victory (there are more "settings" than that on the dial, but that suffices). If it looks like things aren't developing the way I planned I either let it roll or cheat. Whichever feels like the better option at the time.
This sounds to me like you're trying to build to guidelines, but the guidelines aren't very reliable. Hence the need to cheat from time to time.
With 3e though (and more importantly the internets) it seemed more and more DMs were on about "encounter balance" and "rules expectations".
<snip>
DMs didn't just design encounters to wipe the PCs out, or the like, they had expectations about PC levels and numbers, and built encounters to certain difficulties accordingly.
That's not "balance" though, that's "building to what you want".
"Building to what you want" is
exactly what I mean when I talk about encounter-building guidelines, and I've never encountered a poster who both (i) wanted such guidelines, and (ii) didn't mean the same thing as I mean. The only people I've ever encounter who use "encounter guidelines" to mean "building every encounter to party level" are those who are saying they don't want such guidelines.
those guidelines, as well-intended as they have been, also bring unintended consequences that affect the game. If the GM deviates from them on the low or difficult side and the players know of them, that breeds dissatisfaction.
I don't really follow this. The guidelines, in 4e at least, allow you in a reliable way to calculate how difficult an encounter will be, and also other things like how its pacing will work (eg there are guidelines advising on the likely effect of using lots of soldiers, lots of sticky terrain, etc).
The closest the game gets to suggesting actual
encounter mix is on p 104 of the DMG:
For a group of nine encounters, here’s how they might be broken down.
ENCOUNTER DIFFICULTY
Code:
Level of Encounter Number of Encounters
Level – 1 1 encounter
Level + 0 3 encounters, 1 major quest
Level + 1 3 encounters
Level + 3 1 encounter
That's not anything like a rule. It's not even a guideline. It's a suggestion. And notice that it has no suggestion for an encounter of party level +4, yet the DMG expressly contemplates the occurrence of such encounters: on p 123, on the section on tracking and rewarding milestones, it states that:
f the characters overcome an encounter that’s really hard, you can count it as two encounters, so they reach a milestone right away. An encounter that’s four or more levels higher than the characters should count as two encounters.
What 4e offers is not terrific guidance on mixing encounter difficulties, which is fairly basic stuff. It offers reliable tools for measuring the difficulty of encounters, hence enabling the GM to build to what s/he wants. Having become used to this in 4e, the absence of it in another RPG would, for me, count as a reason against GMing that RPG.
I've run GURPS for 20+ years, and there is nothing even remotely like "a way to build combat/scene/encounter/whatzits in a balanced way".
I ran Rolemaster for 19 years and it similarly lacks any sort of encounter-building guidelines. Their existence in 4e was one big attraction for me.
In AD&D I tended to find it fairly hard to build to desired difficulty, in part because the maths is unpredicatable and in part because so many abilities (Petrification, Energy Drain etc) are so swingy.
Rolemaster has fewer swingy abilities (though it still has some, including melee combat in many cases!), but its maths is very unpredicatable, especially because of open-ended rolls and the prevalence of crit tables.
In 4e can build to the desired difficulty in a reliable way, without having to cheat, because the maths is predictable and abilities are not all that swingy (yet, at least in my experience, still interesting and engaging in play).