I have NWN2 Complete and I want to create a character that does sword/shield and uses spells to buff themselves for battle. This is a melee focused character with casting as a secondary attribute.

What classes and skill/stats should I be looking at?

If I wanted to do something like this I would probably be looking at mixing Paladin with divine caster so maybe something like this (BTW handy NWN2 build search engine):

http://nwn2db.com/build/?18044

The nifty thing about Favored soul is that it uses Charisma for spells, when most divine classes use wisdom, and you need charisma anyway for smiting, divine shield, divine might. So you get to use one stat for spell and divine abilities. Downside is it still uses Wisdom for spell DC, but if you are using spells mostly to buff, then DC hardly matters.

Using that same line of thinking, pairing Paladin and Sorcerer to eventually take levels in Eldritch Knight might be to your liking. Charisma is the primary ability for both classes, leaving you enough points to dump a little something into Strength and maybe Wisdom. You can even focus on the school of Transmutation which contains many of your buffing spells that you'll want like Bull's Strength and Eagle's Splendor.

Except that with sword and shield mentioned, I assume he also wants armor which divine casters can wear, and sorcerers can not.

You'll gain those weapon and armor abilities when you take your first level of Paladin. Because you'll be wanting to stroll around in a sweet rig of heavy armor, you'll also want to take the feat Still Spell early on in your character progression to sidestep arcane casting penalties.
https://nwn2.fandom.com/wiki/Still_Spell

I'd look at 3 levels of Paladin to get immunity to fear and disease, then take Sorcerer levels until you gain 3rd level spell casting ability then go all in on Eldritch Knight.

Both options are viable, but IMO Cleric/FS is better for buff and bash, Sor/EK is better for casting offensive spells.

"Divine Power" is the killer divine spell for buff and bash, as it gives the Cleric/FS full fighter BAB and it is actual BAB so it doesn't count toward the AB bonus Cap.

Plus you don't have to waste feats on still spell, making it more likely you get Epic Divine Might. If you are going for Divine Might, IMO it doesn't make any sense to not get Epic Divine Might as it double the duration and damage.

These are all great points and frankly are a more potent package than what I'm suggesting. I mostly just dislike divine casting, so I'm biased. Lol.

Sounds like you want something with some monk. Consider the Sacred Fist prestige class. You only need to reach level one divine spell casting. Once you start taking the prestige class levels, you'll be able to resume your divine spell progression and still get a little of the cool monk stuff.

Paladin mainly gets you "Divine Grace" which is charisma bonus to saving throws, getting rid of Paladin does open up the alignment, and allow Bard into the mix. Bard is good all around character class, and they self buff from both their spells and their Song which can be quite good.

Really so many options in NWN2, poke around in the search engine I linked before...