Artificer issues
 

Been watching a YouTube channel that shows how to create characters from games/comics/TV/etc. via D&D rules. Some use Artificer (Winter Soldier, Demoman, Donatello, etc.)

With the Artificer class selection, there’s three options available.

The problem? Some of the benefits/selections at the various levels are only available with one of the three choices, making it difficult to level up if you have a certain design in mind.

I'm not sure what exactly you're saying the problem is. The Artificer in the Community Pack is designed to follow the Artificer class and subclasses' design. Mixing and matching various subclass features is not supported by the rules of 5e. You'd need to use the editor to make your own version(s) of the subclasses to do that.

To elaborate: subclasses in 5e each have their own unique set of features that you gain as you level. The rules of 5e do not allow you to pick and choose features from different subclasses. You pick your subclass and that's what you get (aside from multiclassing, but even then it's still just one subclass per class). So if whatever channel you're watching is telling you to mix subclass features, they're telling you to not follow the way 5e is designed. That's fine, as house rules and homebrew are a totally valid way to play. But 5e in Hero Lab follows the rules; no mixing subclass features.

I’m saying there are three different Artificer classes on the select class page: Artificer, Artificer (2017) and Artificer (2019). And each has different attributes/bonuses/etc., which can make it difficult if your character “blueprint” is going a certain way.

Oh. That's because you have the Unearthed Arcana Artificers' sources active on your hero. The class that is called simply "Artificer" is the official 5e Artificer.

I don't recommend having every source selected if you don't know what's in them. UA content is unoffiical, often imbalanced and incomplete, and shouldn't be used anyway without DM approval.