Does 'Each player gets a bonus feat' mean that Variant Humans would get 2 feats, or are you then not allowing Variant human? I would not allow it, and make that specific, as 2 feats, likely 3 by level 5, is quite powerful.

Campaign link below.

https://ddb.ac/campaigns/join/18895791537487857

content is shared.

Just my own opinion  - I would also clarify to not allow Critical Roll and UA content....JMO as I feel they are less balanced...

The question now is if this opens up for other contant than just PHB and DMG. If so then I'll put together a character with that in mind.

Yes, if it is DnD beyond content shared in the campaign link it is allowed.

However let's not use 

 Critical Roll and UA content....JMO

How are you ruling the feats then. My suggestion above was to not allow Variant Human or Custom Lineage, as both give a feat as well. If you allow those two, then a player can start with up to 3 feats, 1 for their race, one for their bonus, and a third for their 4th-level asi.

I am good with allowing the variant human, and custom lineage. Since I dialed back on the magic items I want to see how the extra feats play out. I ultimately do want a large variety of character types and a wide range of creativity in the characters so that characters don't get stale or too repetitive. Let's see how it goes. 

Cool! Here's my stats for proof

Ability scores: 15 15 11 15 18 16

Kipp of the Unkillables/Dreamune

Kalashtar totem barbarian that is becoming corrupt from the dreaming dark.

We have our first active match. I am sending a PM to the two players that are up. 

Please describe yourself as you step to the entrance of the arena floor.

Today's Arena is a stone pit 20 feet deep. It is thirty feet across. Both of you are guided to the edge of the pit. The cold, uninviting stone floor below suddenly begins rushing up at you as you are unceremoniously kicked from behind.

Roll a reflex save, or other appropriate skill/action to reduce or avoid falling damage.

A large tortle is pushed into the arena, wear a black cloak that flutters around him as he falls....attempting to land on all fours.  Slow Jack slowly get's up...using his staff to rise to his feet.  In addition to his staff, a couple daggers hang on his shell.  He would appear a normal tortle, unless you see his eyes....black shadows seem to randomly fall across white eyes with no pupil, looking at him reminds one of another realm, a realm of darkness and shadow.

dex save 9

(What kind of prep is allowed?  Long lasting spells  (those with one hour duration or more could be precast for example?)

A fairly large and dark grey skinned half orc falls in about the same time as the tortle. Acting quickly, the dark splint mail wearing man whips his shield about so that the spines covering the face might dig into the wall, and hopefully slow his decent. Even if it doesn't, once he's at the bottom of the pit, he rises chuckling and dusting off the weather beaten clothing beneath where it showed past the plated greaves and guards adorning his frame. "Thanks for dropping me off!" He called up cheerily and smiled broadly.

Then appearing to remember the place he was in, Challub quickly picked up and put back on the part leather and metal helmet that had fallen in the descent over curly black hair, before breaking out one of the many spears secured in a great quiver at his back. 

Dex Save: 16.

For the DM:

 (Also same question as Burgen, if albeit with less magical prep involved.)

Aight I'ma head in.    

Prior to being thrown into the pit you are able to perform one full round of actions.

Burgen received 6 damage from the fall into the pit. 

Mehmen is able to pull off using his spiked shield to slow his fall and lands with grace on his feet.

You can post or if you prefer, pm your prefall actions. Then roll for initiative.

Initiative  11

Initiative: 20.

Prep Action(For DM only, maybe?):

As you now take your actions be sure to describe them. Describe what your character does and follow it up with the appropriate roll.  

Example: Argon swings his sword in a wide arch spinning inward aiming for his opponent's head.

Attack roll:18

Opponent should then respond with whether the attack is successful, or make the appropriate roll for any needed saves. Players should be able to mostly conduct the fight between them. I will continue to watch the post and respond as needed if a DM decision is needed.

Players do not need to disclose their actual stats, but must be honest if an attack or action is successful or not.

Slow Jack is slow...however this time he seems faster than his opponent.  "Welcome to the shadow realm...."  He mutters an arcane word known to those of the shadowfell, and darkness fills the arena.  He steps forward and stops.

Jack casts Darkness using two sorcery points, centered on the center of the arena....

he steps forward 10 feet..slowly.  He is Slow Jack.

(Assuming there is no need for a Perception check since Slow Jack isn't actively Hiding...)

Challub squints, but seeing no change to the darkness, sighs and says, "So, its gonna be one of them fights, eh? Unless, this really is a Shadow -- Know what? No. Just gonna focus on fighting." The half-orc advances on that note, if albeit slowly as to avoid tripping over his own foot. With shield held high and spear out and ready at his side, he reaches a rough point to where he can vaguely hear the Tortle before jabbing away with his spear.

Without eyes to be certain, he hoped to catch the tortle in the center mass or close to it, and pierce that tough shell of theirs. Yet if it hits at all, his attacks glance off. Even the last ditch effort to turn his recovery from overstepping the lunge and bring the butt of the spear to bear is not enough.

Movement: 20ft closer to where he last saw Jack(I guess?).

Action: Attack w/ Spear.
#1 To Hit: 12 For: 11 piercing damage.
#2 To Hit: 19 For: 10 piercing damage.

Bonus Action:Attack w/ Polearm Master Strike
To Hit: 16 For: 7 bludgeoning damage.