Do you have a sense of how magic-heavy the campaign will be? Items like gauntlets of ogre power are uncommon, so they may show up and save you the asi. Otherwise, PAM at 4 should work pretty well. Then you can always delay your decision about level 8 until it happens. Could be you’re doing fine and don’t need the bump. And really, the difference between a 16 and an 18 is +1, roughly 5%, I doubt you’ll notice the difference. You will every time you miss by 1, but that won’t happen very often.
Another thing to consider is a couple half feats. Heavy armor master at 4 (usually, I’m not a huge fan of this, as its value drops as you level, but at 4, you can get some use from it. And if the campaign is only going to 8, you should actually get decent mileage from it). Then at 8, something like slasher/crusher/piercer, depending on what weapon you use.
I want to play an "Oath of Vengeance" Paladin that starts with:
STR 16 DEX 12 CON 16 INT 8 WIS 8 CHA 14
I want to take the "Polearm Master" feat at 4th level (just because it looks like it will be fun).
But I don't know if I should get my Strength up to 18 or get another feat (maybe "Sentinel") at level 8...
I'm afraid that (with my STR 16) I will start to miss a lot of attacks at this level...
What should I do?
I don't think you should increase your strength. Generally you will miss less because proficiency increases you attack bonus even if strength remains flat.
Personally I would boost Charisma at level 8. That will boost all your saves, all your close allies saves, your abjure enemy DC and all your spell DC.
If you are getting PAM I would say Charisma is even more important because of the interplay between reach and Wrathful Smite. With PAM Wrathful Smite is becomes the most OP first level offensive spell in the game. The reason being you attack enemies from 10 feet away and the frightened effect stops them from ever moving closer to you, until they shake the effect. To shake it they need to waste an action to make a wisdom check (not a save). They make the check with disadvantage because they are frightened, so they will almost never break it. Boosting Charisma makes the save and check DC higher and makes your concentration save higher.
STR 16 DEX 12 CON 16 INT 8 WIS 8 CHA 14
Do you have a sense of how magic-heavy the campaign will be? Items like gauntlets of ogre power are uncommon, so they may show up and save you the asi.
Otherwise, PAM at 4 should work pretty well. Then you can always delay your decision about level 8 until it happens. Could be you’re doing fine and don’t need the bump. And really, the difference between a 16 and an 18 is +1, roughly 5%, I doubt you’ll notice the difference. You will every time you miss by 1, but that won’t happen very often.
Another thing to consider is a couple half feats. Heavy armor master at 4 (usually, I’m not a huge fan of this, as its value drops as you level, but at 4, you can get some use from it. And if the campaign is only going to 8, you should actually get decent mileage from it). Then at 8, something like slasher/crusher/piercer, depending on what weapon you use.
I don't think you should increase your strength. Generally you will miss less because proficiency increases you attack bonus even if strength remains flat.
Personally I would boost Charisma at level 8. That will boost all your saves, all your close allies saves, your abjure enemy DC and all your spell DC.
If you are getting PAM I would say Charisma is even more important because of the interplay between reach and Wrathful Smite. With PAM Wrathful Smite is becomes the most OP first level offensive spell in the game. The reason being you attack enemies from 10 feet away and the frightened effect stops them from ever moving closer to you, until they shake the effect. To shake it they need to waste an action to make a wisdom check (not a save). They make the check with disadvantage because they are frightened, so they will almost never break it. Boosting Charisma makes the save and check DC higher and makes your concentration save higher.