Since the SL prepatch, the Starter edition limits had a few very notable changes:
-Gold cap is now 1000 per character.
-Profession limits seem to have been removed (or at least is not mentioned anywhere on blizz's limits on starter edition characters, as seen
here).
Plus, a notable squish had happened, and characters that used to be level 20 were squished to 10 (and level 120s from endgame BFA were squished to level 50, with level cap being level 60 in shadowlands). That said, trials that used to be level 20 but got squished to level 10 can level back up to 20 [and 200% mount speed is available at level 20, including to trials).
Part of the squish included streamlining the leveling process, where anyone can start at any expansion at level 10, and which expansion they level through is their choice.
That ended up allowing level 20s access to all vanilla dungeons, and many dungeons in all other expansions [as long as the dungeon is in a zone who's level floor is 20 or less], among other contents.