I don't stealth. Like I stealth, but I don't care if I get caught. Makes everything more dramatic.

Too late. I'm 10 hours into MGS: SE 3D.

See above. Besides, I like playing games in order.

MGS5 stealth is pretty easy, but the S rank is wack. Its very glitchy, some missions I rush in, get caught, kill a bunch of people, blow up a bunch of stuff and still get the S rank.

Just watch Rambo 2/3. Kojima pretty much ripped off all the mechanics and tactics from them.

Ah, a headshot to the helmet will stun them for a good few seconds, making it easy for you go go up them them and RT/R2 their ass. As long as they are stunned and nobody saw you, it wont count as a ''detection''. 

Aslo, smoke grenades are very important for slipping by the enemies. AI sightlines are rediculously accurate, but the AI it self is really dumb. 

Well, the release order makes the most sense, because that's the order that Kojima came up with the story.

Dress appropriately to the locale, select the time of day appropriate to the mission, equip weapons appropriate to the approach you want to take, scout out possible entry and exit points for objectives, "ive tagged all the enemies so they show up as red markers" isn't proper scouting, you need to scout the area for entry points, places to hide, contingencies and scenarios to react to possible outcomes, properly use air support, properly use weapons, properly take buddys based on the mission at hand, basically just execute the mission with the best possible setup, and properly scout an area.

The dog will help immensely with spotting enemies that you cant.
Horse is good for convoy missions, you can get it to shit on the road and the shit will cause vehicles such as jeeps to spin out, so you dont need to use weapons to stop them.
Quiet is good for missions where you want to either go in guns blazing or need support incase things go south, give her a tranquilizer sniper rifle instead of a dmg based rifle, she will put enemies to sleep if you fuck up and get spotted, but only if she has line of sight to the enemy, make sure shes in place and that you can see her green laser sight.

Crawl like a boss, in the shadows, in the grass, hit triangle to hold your breath, take your dog and have him distract the enemies, if you get noticed but not full on spotted, hit the deck and start moving AWAY from where you were spotted because they will investigate that area and potentially scout around it.

If all else fails, take advantage of the weather conditions, rain and sand storms help with infiltrations immensely.

Oh, and shower every time you go back to home base or the enemies will literally SMELL you.

Taking out everyone isn't necessary. Just a few people. Hell, in mission 3, you can literally just take out 1 guy and not even walk into the base if you have a sniper rifle. It's not a bad thing to just sneak around while people are still alive and walking. You know where they are once they're marked. It's actually kinda fun because of the limited shots you have before your suppressor on your tranq gun wears out.

Shooting them in the neck or wrist will result in the target dropping sooner, if you shoot them elsewhere on a clothed portion, it may not put them to sleep at all or will put them to sleep but will take 15-25 seconds, you can increase the possibility of it working through clothing if you get a traquilizer pistol with a higher penitration stat.

Also, the enemies adapt to the approaches you take as you play, they only start wearing helmets if youve been taking headshots a lot in previous levels/play, at the same time they will also start wearing night vision if you continuously attack at night.

It's a little difficult early on, but once you unlock and upgrade equipment, it becomes easy. You don't have to take out everyone, and you could create a diversion without them finding you.