I love reading on the warforged and feel bad I haven't gotten to pay one yet but glad that I will very very soon and wanted help making a character for my DM's homebrew world, he gave the okay to access whatever I want and we are going to go over my choices after to get the final check mark. My issue is I can't seem to find much conversations on the warforged that came out for the official book rising from the last war so all the current conversations except for a handful seem to be very outdated. So here are my questions and thanks ahead of time for the answers! 

My character concept so far: He will have a calm and occasional smart ass personality, I gave him a mechanical tail, I want to focus more on front line combat, and I want him to be useful out of combat. The party consists of a Kenku Cleric who speaks in phrases he has heard before, a Cowardly Human Monk open hand, A bookworm stone sorcerer Aasimar focusing on melee combat, a bubbly elven moon druid raised outside of civilized land by a dragon, and a perverted Conjuration wizard who hides her smut within her spell book. Hopefully you all can give me some ideas so I can be useful and interesting even with all these full casters lol would hate to feel like I am just there to get hit honestly.

Question 1: What classes do war forged work well for? They seem to be pretty good at all but amazing at none and I really want to be on the front lines with my warforged honestly. (side note, I love that the war forged are great to work around things I don't like about classes like paladin and cleric because instead of getting power from worshipping and what not I can have it flavored as part of of me.)

Question 2: Can warforged get dragon marks? Just wondering, my DM said it would be fine if I came from eborron through planer travel and the ship crashed leaving him inactive for 1000's of years only to be found by the party in a new and mysterious world.

Question 3: aside from classes can I get more specific on sub classes? what would be more interesting?

1. Warforged are good at almost any role, but excel at ones that benefit from high AC due to their innate +1 to AC
2. No, warforged as written cannot get dragonmarks. Only certain races can benefit from dragonmarks due to their bloodlines
3. I find any subclass can be interesting, but it depends a lot on what you like. Heck, a chronurgist warforged would be cool, you could be like the terminator; a machine sent back in time to save the future.

3. Love the Idea but sadly can't afford Wildmount for a good while lol

1. But as for what i like to play, well lets see I love utility and out of combat stuff, I can find joy in bear totem barbarian purely for the shenanigans as a goliath or a firbolg but otherwise meh, idk fighter I have no experience but it seems to lack anything out of combat honestly, Monk is cool but sadly when I want to punch with my fists 70% of the time I want to be a hand to hand barbarian not a jumping monk dex fighter lol. Then as for casters I just love utility over high flashy numbers like I would take enlarge/shrink over fireball any day purely because it's power comes from creativity and fun over "I deal damage, I hit hard" not that there is anything wrong with that but I just like my utility. ((edit)) I love casters purely because of their sheer amount of utility which is why I am so drawn to them... but I feel as if the party has maybe too many casters ranged casters.

2. Ah alright I figured that, I was just curious about that.

Just a quick correction, 12 of the 13 official dragonmarks cannot be put on just any race. Warforged can get the Aberrant Dragonmark feat at your DM's discretion. 

Warforged Rune Knight could be a fun one.  Pick up some flexibility and some pseudo spells.  Also Samurai makes for some decent charisma checks at 7th level or whenever that feature is gained.  Depending on the groups view of multiclassing a little rogue for some skills and occasional sneak attack damage could be a fun perk.  Just gotta have 13 DeX.  Now that I mention that I wonder how a arcane trickster/rune knight would look.

Also, do you have your stat block yet, or are you using point buy or standard array?

we plan to roll 4D6 and remove the lowest 6 times then place them where we choose to, we feel it adds more personality to the character when there is a chance to get like a 6 in one stat and a 20 on another depending on how lucky or unlucky you are lol

Also I almost forgot about rune knight it was like one of the only fighter archetypes that I actually found cool honestly that and eldritch knight due to the out of combat possibilities.

Anyone know of some good caster builds that play like martial casters that can wear plate armor? lol just curious

thanks for the correction lol

Most clerics can wear heavy armor.

Armorer Artificers have heavy armor.

https://ddb.ac/characters/25064124/GAngyW

Just as an example...  also I may use this in the future looks fun.  Not super strong with normal attacks, and not high in strength.  Cool thing is the giant strength for advantage on strength checks, and saves and some bonus damage.  Really good with tools, thieves, Smith, and in this case tinkers.  Knowledgable about magic, I think of it as a magic database.  The storm runs let's you give people advantage on an attack as a reaction which can be used on yourself for easy sneak attack without having to hide (one minute, per short rest).  And 20 ac with medium armor like a breastplate, with a shield equipped.  Then some spells to round it out, mage hand could be a little drone that you send out.  Lots of ways you could make this your own if you so chose.

Keep in mind the full effect takes a bit.  I see it starting as rogue then fighter to 3 then rogue to 3.  After that maybe fighter to 5.  Wouldn't be all bad to just alternate levels till 6, or rush to fighter 5 for the extra attack.  This has got the wheels in my mind a spinning.