I'm very new to D&D (5e) and my first character is a Monk w/ Hermit background, currently level 4 (Way of the Open Hand)

For RP reasons he's only going be unarmed, so obviously I want to wait a bit before multiclassing. I'm think either after level 5 or 8 depending how the campaign progresses.

My goal is to make a battlefield controller that zips around hamstringing casters and assisting our Rogue and Barbarian on the front lines. I already know my first error was taking 2+ Dex instead of the Mobility feat, I plan on taking it at Lvl 8 though.

Anyway, I realized I could save some Ki with free disengages, and add double dashing to my repertoire, by taking 2 lvls of Rogue. I was then looking at the archetypes at lvl 3, and most wouldn't help much since I don't use weapons, but Scout caught my eye with the Skirmish feature (If an enemy ends their turn within 5ft of you, you can use your reaction to move half your movement speed). Plus I think it would be cool for RP reasons for my Monk to be an expert at Nature and Survival.

Do you guys think its worth it? Should I just go straight Monk since I don't get Sneak Attack, and plan on getting Mobility anyway? Would it be better to just go with Swashbuckler and skip the Mobility feat?

The rogue multiclass is mostly redundant for an unarmed monk with the 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. Hence, those 2 or 3 rogue levels would probably be much better spent getting you to a higher monk level instead.

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 Mobility either

You (and your party) should focus your fire, one dead and one alive Ogre 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 Fist works, Mobility 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.