So the bardlock and palock builds have taken a hit in BG3 since the big benefits of the dip in warlock seems to have changed from first level hexblade warlock to 3rd level pact of the tome. This doesn't make them unusable though, just less broken.
The primary reason players used the single level combos was that a character could focus their stats on just Charisma, which meant that they could spend two ASIs on buffing the stat and just take feats for the rest. It also meant that their support and casting abilities didn't have to take a hit in order to be a good melee combatant.
Which bard you choose should be dependent on your goals and the level split you want. Basically, if you want to smack things, you need to get your warlock pact of the blade to the level where you get multi-attack before going lore Bard, or vice versa and do Swords bard until you get multi-attack and switch to pact of the chain or tome for your warlock.
You can do both pact of the blade and swords bard, but you are doubling up on some of the abilities, so it isn't quite as gishy as taking one caster and one martial subclass. However some people don't mind that and really want to double down on the melee and just focus on how hard and fast they can hit things.
Regarding paladin's the general guideline is take 2 levels or 6/7 of Paladin and then warlock the rest of the way. Or with BG3 take 3 levels in Pact of the tome warlock and the rest as Paladin, which will get you the most smites. (2 level 2s instead of 1 level 3 if you went full Paladin.)
So you aren't ruining your character by mixing the two together, especially with 3 pact of the tome warlock and 9 swords bard, you are only losing 1 5th level and your only 6th level spell slots. Which is a tradeoff you will have to make if you want to go SAD with you character and make them a beat stick.
(SAD is an acronym for Single Ability Score, the opposite of MAD, which is a Paladin's main weakness. Here is a breakdown which is probably more than you wanted to know: https://thinkdm.org/2021/11/20/sad/#:~:text=D%26D%20players%20use%20the%20terms,for%20Multiple%20Ability%2DScore%20Dependent. )
