I'm going with custom party and already have two chars set in stone:
Of course Lotus a V-Human - Thief (LVL 12) - Dual wielding hand crossbows and I hope they add Ninjatōs (a variant of short swords) for more flavor to the game. The background will be Criminal for now, as long as they don't add my beloved Faction Agent.
Nyria a V-Human - Trickery Cleric (LVL 4) / Lore Bard (LVL 8) of Waukeen - club with shield + lute and hopefully a blowpipe (to give the coup de grace) for flavor. She will hopefully be a Guild Merchant for either alchemy or gems, as befits a rogue mercenary band.
I will also be joining the Zhentarim. But as of now, it's more Robin Hood-like. We will see how it goes on with the Zhentarim until the end of the game. I plan to accompany them on a better path. I like their "gray" style. At least the smarter ones of them know that they shouldn't be too cruel, because it makes no sense to rule over a graveyard. Dead people don't bring income. I want to use their family ties to do good from the shadows. In their competition, they end up fighting other evil factions. So far, I've been able to make good decisions to do this (e.g., convincing Brem to release Oskar). However, if they really only stand out as abysmally evil later in the game (i.e., from the options available to us), then I'll weed them out and join The Guild instead. Since I'm a mercenary, I can hopefully join several organizations and infiltrate and betray one or the other if necessary.
I don't know the other two character slots yet. I would like to have them filled with non-PHB classes. Currently they would be:
Rakdos a Zariel-Tiefling Berserker all the time throwing enemies and items in his frenzy mode. I would also love to multiclass him with the https://www.5esrd.com/database/classoption/thrown-weapons-master-3pp/
I really love this because it's just something new and varied to the usual ranged combat style with bows or spells. I would also complement it with a slingshot, which is also a strength-based weapon. However, I can also imagine playing him as a Gloomstalker / Blood Hunter (Profane Soul) with Bounty Hunter background. But then I lose the alternative ranged playstyle (frenzy mode for BA ranged attack is just too elemental). I'm also a bit skeptical about Blood Rites, because of Speak with Dead. If I kill every enemy with elemental damage the spell is useless. Well, but these subclasses probably won't find their way into the game yet, and I would have time to test NPCs that are eligible for Speak with Dead during playthroughs. On the other hand I'm thinking about Gandrel (at least Monsterhunter subclass?) and there are rumors about Helia a Werewolf counterpart to Astarion (which implies a BH with Order of the Lycan subclass).
The last slot is currently planned for a Battlemaster Half Orc named Sorin. And there are many other awesome non PHB Classes I cant mentioned too often: Arcane Archer, Raven Knight, Hexblade, Echo Knight, Artificier. You know its difficult, especially with just a limited Party of 4...