virtual guitar, bass, guitar, horns?

I like my Yamaha vl70m module (I think that is the model) with the Patchman chip... the saxes and many other instruments are quite expressive.. I use it with a couple WX-5 wind controllers... worked well with a keyboard too. Not sure how easy the  Patchman 70m is to find though . a used Yamaha Motif is a pretty good one as well.

If you have Studio One then you should have access to Presence, the native sound set. You may need to download ‘Studio One Instruments’ from your Presonus account, if nothing is appearing in your instrument list. You will then at least be able to use Presence sounds as patches for your musical ideas until something better comes along. The string sounds in Presence, IMO, are about as good as you could hope to get without paying silly money for posh sample libraries. The brass and sax sounds are OK, and the guitars kind of disappointing, but you can get some good electric guitar and bass sounds (plus some intriguing ethnic instruments) included in Native Instruments’ free Kontakt Player (you will need to download the ‘Factory Selection’ to get the sounds):
https://www.native-instruments.com/en/p...-5-player/

Kontakt will run as standalone, or integrate with Studio One in the same way as any other VST (I am assuming that you already have the VST add-on for Studio One to be able to load Pianoteq in there).

There are 3 groups doing virtual wind instruments that are way ahead of sample libraries but take a bit of finesse to control (they're that realistic):

The most realistic are probably the horns and saxes from Samplemodeling

There are very good single strings (Violin, Cello, etc) and a bunch of woodwinds of similar expressiveness but varying degrees of authenticity from Audio Modeling who split their SWAM engine instruments off from the above fairly recently.

The most affordable partially-modeled winds (you can still use a breath controller, for example) come from Wallander Instruments whose WIVI Band set gets you a decent starter set for $130.

Most other strings are currently better from sample libraries, such as the guitar stuff from NI mentioned above.

LASS from Audiobro is still the most satisfying of the string ensembles I've used, but it'll cost ya.

I suppose it's worth noting that if you're on a Mac, Logic X ships with a surprisingly comprehensive set of fairly decent samples and synth capability. Some (drums, organs, guitar amp modeling and effects) are very good, others less so..but you get a lot more than you ever used to for a few hundred bucks, along with very good effects, notation and recording capability. Certainly a good way to get started.