Later mods in your list now really win, maps can bring shader libraries under any number, and the launcher refuses content that needs a newer launcher.
Load order follows your list. The list always said later mods win when two
of them change the same thing, but the launcher's file names made the first one
win for most mods. Each mod now loads by its place in the list, so the one lower
down wins, as the list says. If you ordered mods to work around the old
behaviour, check that order.
Maps can use any shader library number. The launcher gives each installed
container a number of its own and renames its shader library to match, so two
maps built under the same number both draw correctly. This is what Halo 2 and
later remasters need.
Added
A newer launcher, when content needs one. A map or mod that needs this
launcher or a later one tells you to update the launcher, instead of failing
quietly. Older launchers are kept on the releases they can use.
Local builds, for people making maps. Builds installed with
mjolnir dev install load above everything from the hub. They show under
Local builds on the My Mods page with a Remove button. The page also lists
any container in your game folder that loses to a copy from the hub, so a test
build that never loads is easy to spot.