PATCH 11.2 AND SEASON 3 NOW LIVE, CHANGES TO BANK, BIS RINGS, ETC.
Legion Remix (or Lemix) is a new game mode. This puts the player in an altered timeline set in the Legion expansion, where their artifacts and power gain work differently. There's not any normal way to turn off your experience in Legion Remix, but if behavior is consistent with Pandaria Remix (and what we know from PTR), we can expect the following:
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.
Instead of the tinkers, gems, and cogwheels of MoP Remix, special powers are attached to trinkets, necks, and rings. These become unlocked at level 20, which means players should be able to use them with a F2P toon.
This is unlocked at level 80, so there is a finite limit to the amount of power level 20s have. That said, there's apparently a finite limit to Infinite Power in general.
Most of the new stuff has no level requirement, and much of the existing Legion collectables do not have level requirements either.
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.
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.
Once we know what's going on, expect this section to feature best jewelry for level 20, and any trick and tips for twinking as F2P in Lemix.
NOTE: As of writing this, the "Terror From Below" jewelry tooltip reports a higher damage done than in practice on PTR. The one on the right that's pulled from the artifact tree more accurately depicts the amount of damage done by this ability. It is unknown which one is the intended damage done, but I assume it isn't the 5.6k damage tooltip.