Best Subclasses? *He kinda likes the Swashbuckler and Arcane Trickster.
Swashbuckler is the best rogue subclass in terms of damage output per round, at least on paper. Arcane Trickster has some excellent utility by virtue of being a spellcaster, even if their spells are very limited. Access to Fond Familiar is especially useful. Thief is a very strong option, particularly due to Fast Hands, though this feature’s value is diminished if the DM is already pretty generous with item use in combat. Assassin looks very attractive because of the auto-crit against surprised targets, but in practice it’s too situational for what it does, and the subclass doesn’t get much else. Scout is a good option if you want to go for a ranged build instead of dual-weapon.
Anything with a Dex bonus will do. Lightfoot Halfling and Wood Elf are both primo choices due to +2 Dex and expanded Stealth capability (again, devalued somewhat if the DM is already generous with requirements for hiding). Half-elf is pretty good especially if you’re going Arcane Trickster because they can be a bit MaD, and +2 Cha and two floating +1s is excellent. Variant human, as always, is a very strong choice. I recommend Mobile or Crossbow Expert as your 1st level Feat, though Skulker is also a solid option.
Anything is fine, really. Criminal is very thematic and the Underworld Contact feature could theoretically be pretty useful if the DM does anything with it. Sailor (Pirate) gives a very valuable feature in Bad Reputation, and is on-point for a Swashbuckler. Guild Artisan (Merchant) is an excellent choice if the DM will allow you to take the mule and cart in your starting equipment.
There are basically two optimal paths you can take here - dual-wielding, which has the higher DPR potential, or ranged, which is the safer option defensively. But also, you really can’t go wrong as long as you’re getting those Sneak Attacks in.
For dual-wielding, you ideally want to take the Swashbuckler subclass or the Mobile Feat. You’ll use hit-and run tactics. If you can get Advantage on attacks against a creature, go for that, if not go for a target that’s adjacent to one of your allies. If your first attack hits, run for cover and use your bonus action to hide if you can, or dash if you can’t. If your first attack misses, use your bonus action to attack with your other weapon and run for cover. If your second attack misses, just hope they target your ally instead of you.
If you want to go ranged, you’ll basically want to stick to cover, use your action to attack enemies that you can get advantage against or that are next to your allies, and your bonus action to hide. Take Crossbow Expert when you get the chance so you can make a second attack with your bonus action if your first attack misses. Consider taking Sharpshooter to get around cover, but don’t use the -5 to hit +10 to damage option unless you have advantage cause Sneak Attack makes that -5 hurt you more than it does other classes.
Arcane Tricksters have a third option with Booming Blade as your action, disengage as your bonus action so they take more damage if they follow you. Gets better with Mobile so you can save your bonus action for Mage Hand Ledgermain.
Another option, if you’re less concerned with pure white-room DPR is to be the party’s
sacrificial lamb forward scout. This is where I think the Thief subclass really shines. Dungeon Delver, Observant, and Skulker are excellent choices for this style of rogue.