There is absolutely no reason for this 'Mech to exist in MWO. In tabletop, the 4N trades out some missiles for some extra heat sinks, which is actually useful if you're sticking to stock builds as the 3F runs hot. In MWO where you can completely customize your robot and put DHS on it, there's no need for the 4N. It's the 3F with fewer hardpoints and worse torso twist, and unlike the 3H, it doesn't have anything unique to balance it out. It's frankly baffling that, when there were already four other Stalker variants, PGI decided to throw a fifth one in there that's just objectively worse with no redeeming features. To reiterate: If you can build it on a 4N, you can build it on a 3F and have better torso twist. It can do absolutely nothing unique. Please do not spend your hard earned C-Bills on it. I realize that my stance on the Yen Lo Wang being useless wasn't popular, but please be assured this isn't the same thing. I'm not letting personal preference influence the way I'm presenting this 'Mech to you. It is in every sense inferior to other Stalkers rather than unique with quirks I don't like.
The 5S is a 3F with worse torso twist and two AMS hardpoints. It's the most expensive Stalker as it comes with an XL engine, which, as mentioned, you should yank out and replace with a normal engine as soon as humanly possible or you can expect to die horribly. The XL255 is a useful engine for Spiders and for the Cataphract 4X, though, so at least it'll see use somewhere. Because of the reduced twist and the AMS points, the 5S can serve well as a proper support sniper. I've seen a pair of them chew up huge salvoes of LRMs, keeping themselves and the rest of the team protected while they return fire of a more direct sort. Here's how I like to run mine.
If you find it a bit hot, swap the ER PPCs out for a couple of regular PPCs. Double AMS means you're going to shoot down the vast majority of missiles anyone decides to lob at you, and a pair of these working together is nearly impossible to hit with LRMs. In terms of weapon groupings, I like to put the left arm and right arm weapons in separate groups, a group for just the ER PPCs, and then one for the PPCs. That lets you take advantage of cover and just shoot one arm around a corner, lets you fire just the ERs at extreme range and up close, and just fire the regular PPCs when you're hot. If you're playing this right, you WILL get hot and you WILL shut down. With practice, you can peep over a ridge, slam the throttle to reverse, pop off your shots and shut down as you're dropping back behind cover.
The 5M loses the side torso laser mounts of other Stalkers and replaces them with a single CT one, and also adds an extra side torso missile port. It's one of very few stock 'Mechs to come with DHS, which is a nice addition. With the 5M, you can cram on nearly as many missiles as the Catapult A1, but with 20 extra tons to play with and five energy mounts as well. Originally, the second left torso missile launcher would fire out of the NARC tube. These days, it fires out of the SRM tubes, so anything up to an SRM6 will fire in a single volley. It retains the limited torso twist of all the non-3F stalkers, so it's not great for brawling, but it can be an absolute pain in the backside to deal with if you do something like this.
It's a bit of a bracket build, and I suppose you COULD just use medium lasers instead of large lasers, but I rather like large lasers in this context. You can reach out and touch someone to a nice distance, and anyone getting within 270 m of you is going to have to deal with some serious hurt. Lights especially will need to be wary of you with the BAP on there.
The real odd one out of the Stalkers, the Misery comes with five energy slots (arranged like the 5M across the arms and center), a single missile slot in the right torso, and the big surprise of a ballistic hardpoint in the left torso. I've talked about the Misery's value for money over here, so I'll just briefly reiterate that you are certainly NOT getting what you pay for in terms of components at 6375 MC. You won't find an XL engine, DHS, endo or ferro here. Really, what you're buying with the Misery is the ability to use a ballistic on a Stalker, so any build I talk about here should be one that makes use of it.
This build gives you a large laser to use as you close and a serious punch inside of 270 m. Honestly, this thing is probably a bit MORE worrying than the Rhino, because it's way easier to get that 49 points of damage onto the same component with an AC/20 than it is with SRMs flying all over the place. Most people seem to be running the Misery with PPCs and a gauss rifle, but that's a wee bit riskier than I like personally. If you want to run a few PPCs and a gauss, then you're generally looking at an XL engine. If you're doing that, it feels like a really bad idea to run a 'Mech that requires you to keep the explosive gauss rifle in the enormous side torso. Being able to nail someone at 540 m with 55 points of damage is almost certainly worth the risk, I suppose, but it makes for pretty conservative play, which isn't really my thing.
That's the Stalker then, a big, scary bastard of a 'Mech. It can't stand there and tank damage like an Atlas, but it can absolutely POUR on the firepower. Even having a side torso go flying off will leave you as well (or better) equipped than a lot of mediums and heavies. Just steer clear of that baffling 4N (and probably the 3H unless you really like LRMs), and you'll have a great time.