Is there a size that is more versatile than others? And is there a size that has more options of music to play? Thanks again, everyone!
Most of the ukulele learning resources and music resources are going to be with the GCEA tuning used in soprano, concert, or tenor sizes. That said, you could use any of that and play it on baritone. It's just you'd be in a different key with the baritone.
I'm wondering what size uke you heard being played. That one captured your attention, so it's worth noting.
I'd say the larger the uke the more versatile it's going to be since you will have more range and notes that are easily accessible. It really depends on what you want to do. If you want to just strum and play accompaniment then any size will do fine. If you want to get into some complex instrumental finger style music or something you may be better off with the added range of the larger sizes.
Also, all other things being equal between instruments, the larger the size the deeper the sound.
You'll also want to research low G vs. high G tuning, if you haven't already. A low tuned tenor would sound more guitar like than a standard tuned tenor.
Definitely buy from somewhere that offers a setup along with the purchase, so you'll get a good playing instrument to start with. Some places have already been mentioned here, and I'll add Elderly Instruments to the list too. Although, if you can find what you want at one of the smaller places like Uke Republic or Mim's, I think I would go there. For your $200 budget you can get a very decent instrument. I think I'd be looking at Kala personally. If you decide to go with a tenor or soprano, then I also recommend the Outdoor Ukulele if you're good with a more durable worry-free instrument made of polycarbonate in the USA. Both come in well under your budget.
I hope you find a uke that works well for you and enjoy it greatly!