If I multiclass my unarmed monk into rogue, which archetype is best suited for unarmed combat?

Question

Goal: Battlefield controller able to zip around stunning casters and offering help to Assassin/fighter and Barbarian/fighter melee.

The strategy I plan on using is having my Monk run to the back and stun the biggest threat caster, so ranged can take them out easier. Next, help the Melee dps with help/proning/grappling/stunning. All the while I hope to avoid damage with superior movement and denying opportunity attacks.

I'm level 4 Genasi (earth) Monk currently and feel like I messed up by taking an ASI instead of the Mobile feat. My group plans to play to 20 and beyond, but I'm not optimizing for damage just utility and mobility. My plan is to go either 17 Monk/3 Rogue, or 20 Monk.

My question is mostly:
If I do dip into rogue, what would be the best archetype for an unarmed monk?

The one that interested me the most is Scout as I really think the Skirmisher feature is good for what I want to do as well as the free expertise.

The only restriction on my character is an RP one: No weapons, armor, or magic, but can use enchanted items.

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Group: We're all level 4 currently using DnD Beyond so all material are available, and only the Gunslinger has any experience.

Healer: Cleric (Life Domain)

Ranged DPS: Ranger/Fighter/Gloom Stalker & Fighter/Gunslinger

Melee DPS: Barbarian/Fighter(Path of the Totem[Bear]) & Fighter/Rogue(Assassin)

Caster: Wizard (School of Divination)

Answer 1

Don't go Rogue if you don't use Sneak Attack

Most of the other features can be replicated with Ki points.

Fights are usually not longer than 3 rounds, so it is 3 Ki points per fight for disengage. This is exactly as many as you lose by spending (wasting) 3 levels on Swashbuckler.
This of course depends on the number of encounters your DM usually uses.

The main reason for a Monk to multiclass to Rogue is Sneak Arrack.

Don't take the Mobile feat either

You (and your party) should focus your fire, one Ogre dead and one alive deals half as much damage as two wounded ones.

The only good reason to run around on the battlefield is to stun as many opponents as possible.
If Stunning Strike works, the Mobile feat is not needed to avoid opportunity attacks, if not, you should stay and keep trying.
The best assistance you can provide to the Rogue (besides stunning) is staying next to his target to trigger his Sneak Attack.

Scout's Skirmisher

DnD is a team sport; if the enemy can't get to you, they will just beat up your friends instead. The net outcome for your party does not change, unless your AC is significantly lower than the other's.
That should not be the case, if you did point buy.

Answer 2

The rogue multiclass is mostly redundant for an unarmed monk with the Mobile feat

You seem to mainly be interested in the rogue multiclass for the class's abilities to dash and disengage. However, the Mobile feat already gives you most of what you want, without requiring a multiclass which would slow down your monk class progression. With the feat, you can "disengage" from a single enemy for the cost of one attack, which is cheap for a monk.

The combination of the speed increase from the feat and the monk's Unarmored Movement ability means that by 10th level, your speed is increased by a total of 30 extra feet, which means you are effectively "dashing" every turn automatically, since you are now twice as fast as the average humanoid. And on the rare occasions that you need more than that, you can spend a ki point to dash and move another 60 feet as a bonus action.

Given all this, the rogue's Cunning Action ability and the Scout rogue's Skirmish feature are mostly redundant. Being able to dash or disengage as a bonus action at will would definitely make it easier to plan your turns, but as long as you don't mind thinking through all the mechanics, you can still accomplish most of the same things with only monk class features and the Mobile feat, and still have your bonus action available for an additional attack or flurry most of the time.

And as you say, with unarmed strikes, you won't be able to take advantage of the rogue's sneak attack feature, which means that your 2 or 3 levels of rogue will do almost nothing to increase your damage output in combat (and that will put you 2 or 3 levels behind the rest of your party and level-appropriate enemies).

Hence, those rogue levels would probably be much better spent getting you to a higher monk level instead.

Answer 3

Mastermind, Scout or Swashbuckler

Mastermind

Mastermind gets the ability Master of Tactics

Starting at 3rd level, you can use the Help action as a bonus action. Additionally, when you use the Help action to aid an ally in attacking a creature, the target of that attack can be within 30 feet of you, rather than within 5 feet of you, if the target can see or hear you.

This means you can easily avoid those reactions and getting too close to melee fighters by using Help at range.

Scout

Scout gets the ability Skirmisher

Starting at 3rd level, you are difficult to pin down during a fight. You can move up to half your speed as a reaction when an enemy ends its turn within 5 feet of you. This movement doesn't provoke opportunity attacks.

This is an easy way not only to not get hit on the enemies turn, but to re-position yourself in preparation for your own.

Swashbuckler

Swashbuckler gets two good abilities for your build. Firstly, Fancy Footwork

When you choose this archetype at 3rd level, you learn how to land a strike and then slip away without reprisal. During your turn, if you make a melee attack against a creature, that creature can't make opportunity attacks against you for the rest of your turn.

This is one of the good ways to escape reactions, and without spending Ki or depending on you hitting. Their other ability is Rakish Audacity

Starting at 3rd level, your confidence propels you into battle. You can give yourself a bonus to your initiative rolls equal to your Charisma modifier.

You also gain an additional way to use your Sneak Attack; you don't need advantage on the attack roll to use your Sneak Attack against a creature if you are within 5 feet of it, no other creatures are within 5 feet of you, and you don't have disadvantage on the attack roll. All the other rules for Sneak Attack still apply to you.

This means you will more often be able to act before your allies, for setting up stuns etc. It also allows your sneak attack to be more useful when you go to take out that isolated mage.

How about fighter?

If you are looking to dart around and inflict status effects, I would recommend a dip into Fighter.

First you get Second wind, for a self heal in case you don't escape from reactions. You do end up wasting the fighting style, as you have decided no weapons or armour, though you may be able to swing it with your DM that you can use dueling with your fists as monk weapons, especially as the self imposed rules are quite strict.

You then gain an action surge, most useful for a Dash or more hits, but also useful for other features that need an action.

Then you take the Battle Master archetype for the maneuvers, allowing you to possibly disarm/prone, whichever you choose, and they often add to damage too which is a nice little bonus.