Stats: Strength, Con, Charisma. With Vuman you can run 16Str, 14Con, 16Cha
Fighting Style: Dueling for damage, Defense for defense (duh), or Blind Fighting to lean more into the "watcher" idea (bonus points if you think your party will be utilizing darkness/heavy obscurement strats)
Feat options:
- Polearm Master: priority 1 here. Gives a good reaction usage, and bonus action usage to maximize smiting opportunities and Divine Favor damage if you use that.
- Resilient: Constitution: If the free feat you get at level 1 stacks with vuman, pick this up as well. Proficiency in Constitution saving throws with the plus 1 lets you finagle your stats (assuming Point Buy) to 16Str, 16Con, 16Cha at lvl1 with a whopping +9 Con save (autopass on DC10) at level 6.
- Inspiring Leader: Level + Charisma mod thp per person per short rest. Fantastic feat if you want a more supportive build
- Sentinel: Good for a protector build, as you can more heavily disincentivize running away from you and toward your backline

ASI preference: Strength -> Charisma -> Constitution (an argument can be made for increasing Charisma first and leaving Strength at a respectable 16)

Spells: Whatever you want, but probably Bless, Protection from Evil/Good, Divine Favor, Branding Smite (lean into Watchers) and the other regular pally spells.

Assuming the feats stack, allowing you two feats at level one, and you take Polearm Master, Resilient: Constitution, and +2 Str, you're looking at 18Str, 16Con, 16Cha at level 6 with +9 Con saves. Damage is decent with Dueling and Divine Favor at ~13 per hit for main attack and ~12 per hit for bonus action attack assuming hits. Assuming 3x hits, that's 38/round. Not bad. Realistically with 65% accuracy it won't be that high, but smites and crits can push it closeish.

If you can guarantee an early strength item (Gauntlets of Ogre Power or a Belt of x Giant Strength), you can put strength a little lower and not put ASIs into it, but that is unlikely for most people.