Yes, the Letters, Numbers Spaces, Special Characters is one of the conventions in D4. But its important to remember thats not the ‘naming’ convention. If I knew the naming convention I would tell you but since the game hasn’t released I can’t. Soon though.
Your name can be whatever you want, can name all of your characters the same thing if you want. Your character name is what’s shown in game to other players, not your battletag
I use the same naming convention I have used for over 25 years - going all the way back to Ultima Online. I used help a guy run play by mail games. So, I use my DM name from those days LAWPRE as my first character. Subsequent alts are ERPWAL (the first one backwards). Then, I go with anagrams from there.