How do I evaluate the power of alternatives to the standard array?

Question

I'm gonna soon DM my first game in 10 years. I have zero experience in DMing in D&D 5e. At each session, four players will seat around the table.

My future players already said and repeated they disliked the standard array because it offers no way to get a stat at 20 at level 4, if they take the first ASI (and thus no feat). And they like to roll. In every other game I played with them, we rolled, and we like that.

On the other side, I'm looking for fairness among the group. I don't want that one player has 2 scores with 18 and another player has only a 14 as their best value.

We never minded being a tad OP as we're mostly in for the story, not for the combat, even though we like it. Also, given that what my players will see are their own stats, potentially going to 20 at level 4, I can use this as a a psychological factor and throw encounters that are just a tad stronger at them as well. They'll be happy with their stats, but still get similar challenges.

1. I've read on the internet that some DMs take the standard array and add 2 to each score. Now this feel really, really OP, so I've thought about adding only 1 instead. This has the advantage of being able to reach 20 at level 4. However, my players will then not roll. I don't really know how OP this is. In average, it gives +3 mod.

2. I homebrewed a bit myself and thought why not let them all roll their own array (4d6, keep 3), then I let them decide which of the rolled arrays they take, but they all take the same array, and they must all agree. There is no fallback in case they dislike each array. This has the advantage of letting them roll, I'm satisfied as everybody has the same base scores and on top of that, I'm potentially putting them in front of a difficult choice: take this min-maxed-like 17, 14, 11, x, x, x array or that MAD-friendly 15, 15, 14, 12, x, x array. They can also be thankful for the one player who rolled 18, 17, x, x, x, x, or be all sorry because none of them did a great roll. Since the players choose, they're responsible for it.

3. I didn't forget the point-buy, I'd allow 33 points (instead of 27) to buy and they can go up to 16, but buying from 15 to 16 costs 3 points. This feels like it's below the stronger array in the first option, for instance. To a min-maxer, it gives +2 stat mods in crucial stats, but to a thoughtful player, it potentially gives +4 stat mod. Pros: 16 is a guaranteed in. Cons: no rolls.

Now, all those methods really feel like my players will be above the average campaigns players (which, in turn, are above the average guy in the in-universe world). I know that. But I would like to know in what measure.

Note: I'm not asking for advice about those alternatives (though they're welcome), but to evaluate -- or tell me how to evaluate -- how OP any of these options will be.

Answer 1

The issues you might have

This is written assuming you go for method 1 or 3, or you go for method 2 and the players roll a good set of stats. Personally, I'd avoid method 2, since it has a lot of ways to go wrong that nobody would be happy with; if you want to give them a powerful array, just let them have one that you decide on, and then you know what level they're on.

Increased power level

In general, letting the PCs have higher stats like this - and all of your proposed methods let them potentially start with an 18, assuming an appropriate race - allows the PCs to have about a +1 to hit and a +1 to damage. This makes them a bit over 5% stronger offensively, and probably another 5-10% stronger defensively because of increased saves and hit points. This probably equates to about .5 of a CR in terms of how challenging encounters will be.

Skill check DCs are by comparison easy to adjust - just expect your players to always get 1 higher than average characters of equivalent level.

Flatter top end

If everyone is special, nobody is. That is to say, if everyone gets to start with an 18 in the stat that they care about, it's not nearly as special when somebody reaches 20. Bear in mind that the items and abilities that set your ability scored are designed with "standard" player characters in mind, so a wild-shaping druid may feel underwhelming since their wild shapes are less effective than other players, and items like the amulet of health are less wondrous.

Feats everywhere

With the need for ASICs to be spent on stats massively reduced, your players will definitely want to take more feats. Some feats (such as Sharpshooter) are massively beneficial in combat, sufficiently so that if they play things smart they might be hitting a full CR above their level.

So what do I do?

There are a few paths; feel free to mix and match from these options as well.

Adjust the world upwards

The most obvious option is just to deal with it by making things a little harder. You'll probably have to adjust monsters upward occasionally - tweak a few monsters by giving them a unique description and bumping their attacks or defences up by a point, and maybe an extra HD or so.

I'd advise being clear with your players that they're building powerful characters and that you plan to challenge them appropriately from the start.

Let it roll

Specifically, let the players be slightly overpowered. D&D is already positioned for the players to be the heroes overcoming evil; they'll have a slightly easier time of it than most, but they may well enjoy that. You may find this frustrating as a GM if your encounters have difficulty challenging them, but a difference of +/- 1 shouldn't be that bad.

Reset expectations

Tell your players that you want to run a campaign at the standard power level. Make it clear that they're not expected to have or need "optimal" ability scores, and that the standard array/standard point buy will not impede their ability to be adventurers.

Answer 2

I have run D&D since the first edition and rolls were always the bane of my existence. From rolling 4 dice, 5 dice, roll 4 characters and pick the best set. No matter which you pick not everyone is going to be even with the other players in the party.

The best way I found to let players get high scores is to do point buy and just give them enough points to make everyone happy, including yourself.

Keep in mind that if the players are hitting +4 and +5 in multiple stats that you will have to bump up your encounters one or two levels. Those stat bumps are like getting a free level.