This was the way to twink back in MoP Remix. In other words, you'll need to have an account without a subscription attached to it. Most of the new stuff has no level requirement, and much of the existing Legion collectables do not have level requirements either.

This is explained a bit more in the next sections, but since a bulk of the player power is restricted to max level, you won't witness the same levels of absurdity that made lv20 priests so popular in the Mists of Pandaria Remix. That isn't a death sentence for the category, though.

There doesn't seem to be any restrictions outside of the 24-hour period, and the gear you are placed in is somewhat low item level. NOTE: This is currently bugged and thus disabled.

I don't blame them for not wanting to navigate the logistics of...everything Legion relevant with Evokers. So, you cannot make one, and you can't set up a lv10/11 Evoker Twink with Lemix.

Infinite Power ("Infinite" presumably referring to the Dragonflight's name instead of the word itself) is the main form of currency for power. You use this to spend points on the artifact tree to get the associated powers. However, when you pick up mementos (the primary source of IP), you also gain stamina. This means that 20s can have a LOT of stamina.

The final trait of the Artifact Weapon Trait Tree is Limits Unbound, which gives primary stat, stamina, and 1% versatility per point. This is unlocked at level 80, so there is a finite limit to the amount of power level 20s have. Since this is the only source of versatility from the system, you will be sitting at 0% as a F2P unless you pick specific races (HM Tauren get a 1% base versa).

Fragmented Mementos are collected from group content, and when you collect 100, they can be combined to give you a buttload of infinite power and stamina. This makes getting that max IP cap easier to achieve, and pushes the viability of F2P 20s in Lemix further.

You will collect Artifactum Sand in Legion Remix - this is used to upgrade the item level of your weapon, which in turn increases your power. The intended cap is ilvl95 for a level 20 in epic gear, but there was a bug in early Lemix that allowed for higher item levels on weapons. 

The consumable buffs (the raid buff scrolls) come back in Legion Remix, but the fact that these powers scale with Attack Power and Spell Power might mean that some classes and races have an edge over others - for example, Orcs with Blood Fury, and as we will discuss later, tanks in general.

Uncommon gear gives one rank, Rare gives two ranks, and Epic gives three ranks. The difference between jewelry item levels stat-wise is simply increased stamina. This means you should aim to get Epic jewelry, and a lower item level Epic jewelry piece is better than a higher item level green. 

You can only wear one of each jewelry piece. However, the artifact powers can be spread across other piece types. Basically, you can't wear two of the same ring, but you can wear a ring and a trinket that have the same power.

Once you hit level 20, you are able to get a free piece of epic jewelry daily near the scrapper. This is great for gearing your twink until you have all the pieces you want. Note you cannot choose what piece you get.

Hemet Nesingwary XVII and Grandmaster Jakkus sell mounts. There are a handful of level 45+ only mounts, but the majority are usable below that level requirement.

These are sold by Horos (link to his stock here). The vast majority are usable by 10+, except for a couple level 45 toys and a quest item.

Anything crafted or obtained via Professions is not available in Lemix in any capacity to anyone.

Outside of some requiring items only available to high level raids to buy, all ensembles should be usable.