Ishnu’alah , fellow Druid of the Claw.
I hope that I may be able to offer some insight into the druids that do the dirty work of being frontliners and more. So a couple things.
Grizzly Hills would not be a good place for Night Elf to be born , especially since Night Elves had very limited presence in the area , we literally just planted a tree and later destroyed when it became corrupted. The areas worth considering for birthplace would be entirety of Northern Kalimdor and Stonetalon Mountains as we see Night Elf settlements. Maybe Feralas would be an option too but I am not sure when original Feathermoon Stronghold was built so it may suffer from same problem as late World Tree. Azuremyst Isles are not completely out of question as we see a very small Kaldorei presence there before Draenei came.
Age seems fine , it widely considered by Night Elf RP community that Kaldorei are considered adult by their society when they reach age of around 300 , though they physically stop to grow roughly around the age of 20. Though keep in mind not all agree with it and we lack lore that would point us in the right way.
As far as Artifacts go - claiming them to be THE Artifacts would be no-no obviously. However simply using them as visual reference is all good. Kaldorei are know to keep the fangs of their fallen Nightsabres so having them fashioned into daggers seems a very fitting idea.
As for acctual cat/bear form. I would advise against using most skins apart from the basic ones (And their colour variants) and Nighthold Feral form. Argument can be made about Might of Grizzlemaw skin for Guaridan but I would be very hesitant about them since we have no real idea what we are actually looking at.
Skins we get from Class Campaign , Stone Bear and Wood Cat could be used to RP as forest spirit while PvP skins make for great NPC model when we are dealing with Nightmare.
Staying in bear form is a tricky question. Above all , you should always have a reason for shapeshifting. Then again , training and mastering the form is very much a valid reason to shift. Could be that you are hanging out in a form so to become accustomed to all the new sensations that world throws at your new and aliens sense so that when time comes , you will not be distracted and confused by the smell of gunpowder , clutter of machines and so on. In one of my stories Neiven shifted into a bear to protect a human from cold winds of Northrend while they were waiting for weather to get better and rescue teams could find them.
There is however inherent danger of staying in form for too long and loosing one’s true self. You are Druid and Night Elf first and foremost. And the danger of becoming Feralkin is something that gets hammered into a head of any young druid. However that can be also seen as reason to spend more time in a form in controlled environment to help you recognize when you are going too far. And there are druids who will shapeshift for little reasons. If you walk around other races during… a fair for example… quickly switching into a bear and cat to entertain children… doesn’t seem all that bad reason , especially considering times our characters live in.
And one last word of advice , allow yourself to learn. Find players that can offer you honest critique and guide you in a right direction.