Warforged echo knight questions

I'm playing my first dnd campaign and just got to level 3! I choose echo knight as my fighter subclass but have some questions

Could I use echo avatar during sentry rest because I'm still aware but immobile?

Can I use my echo to do strength checks like breaking a door?

Can echos hold objects if they are handed to them?

Do echos trigger traps? (my dm loves traps)

Can you teleport out of being grappled with your echo?

Can echos go under water?

Do echo keep racial bonuses? (Like advantage on poison saving rolls)

You can always teleport out of a grapple

The Echo can attack and take shove actions (which is an attack action)  So yes it should be able to break down a door

The Echoe occupies a space so it should trigger traps, though it's weight is debatable if we are talking about pressure plates and questionable if it counts as creature for triggering spell traps.

There is nothing that states that the Echo can't go underwater, it can move just like other creatures do.

The Echo uses your saving throws it says nothing about racial bonuses though it's immune to all conditions.

The Echo should last through your rest, the incapacitated condition ends your Echo but it can't see anything until you gain the echo avatar at level 7.  But your warforged can see and hear normally during it's sentries rest so I don't know what you are trying to gain from this.  The Echo does not roll it's own perception checks or anything like that.

Carrying objects is up to your DM, I like my players to be creative so if someone would hand their Echo a bomb and run to the enemy as a suicide bomber I'd be fine with that

There’s a long running thread in the fighter forum you might want to check out that’s gets into echo knights. There’s a lot of wiggle room in exactly how they work, so you’ll really need to hash things out with your DM, including asking these same questions to them. It’s way better to ask between sessions, so you Dm can spend time reviewing the rules and thinking about them, and then you’ll both be on the same page about how they work. 

https://www.dndbeyond.com/forums/class-forums/fighter/64918-an-echo-knight-faq-frequently-asked-questions

Appreciate the help, I was thinking I could use the echo as a sort of gaurd while in sentry rest in a tight spot.

Thanks for the link, I'm new to here so it's very helpful. Will definitely be using this to clear things up with my dm

I appreciate the criticism. My dm seemed to like my pick of subclass so I don't think he's upset by it but I so have some questions, what's misty step? Does counter spell even work on echo summon seeing as how it's not technically called a spell and if so how would that work? Also you could try using an anit magic field or a city where magic is outlawed/ banned and would have people throwing things at his echo (as the lots of small projectiles would probally kill it fast) that sounds like fun

I think a lot of the jank of the Echo Knight can be easily avoided by just playing it straight. The echo is you from the future or whatever. There's no reason it should be able to fly, for example, so the only reason a DM would have to deal with the silly flying nonsense is if the player isn't playing according to the fiction, but instead trying to exploit the rules.

Yes, this is sort of offloading the work of fixing the design onto the player. I don't endorse the Echo Knight, for this reason. But I don't think it's quite as much of a problem as people online wanna say it is.

You'll still have some jank, of course. 

While sure it's strong on paper, I haven't found it to totally break encounters any more than an aarakocra does. Or a spellcaster, for that matter. People just get upset when a fighter can do more than walk and swing its sword.

The ability to block a passageway for a large creature with an echo, requiring a melee attack to attempt to clear the echo cost an attack and no damage is done on the player is broken.

It doesn't block passage. It's an image and nothing says creatures can't move through it. The thread isn't long because its broken, the thread is long because the echo is not stated as a creature or an object, leaving a LOT of interactions very fuzzy.