Well the best thing about Kontakt is its not a synth. You're not simulating a sound or trying to make a synth sound like a guitar, you're using sampled recorded samples that are trigged by the midi patterns or by your keyboard. So that's why it's a must for orchestral musicians who want to sound like they have a symphony, or for musicians who want to sound like they have a drummer or a bassist. It's a little weird setting up in FL studio so don't be surprised if you need to do special setups or change the color of your piano patterns before they start playing.
Biggest issue is you need good libraries to have an instrument sound authentic, that requires a LOT of samples and a decent size library for every instrument or orchestra you need. A flute, bassoon, violin, etc can be a different library for each or a big library to use. Kontakt, like your DAW, is just the delivery system to make it happen, its not making the sounds, its just unlocking your access to the sound library to make that happen. A library may be 4-45 GB a piece. You may want a few different sounding drum kits instead of just one for example. Each library costs lots of money so your budget will be in a world of hurt if you go that direction (and your Kontakt isn't cracked). Getting Komplete is not a bad way to get a chunk of this (and great synths) all in one shot.
Here's a few recommended ones i threw in a list from MLR recommendations along with some vids on each in use. This way you can see a few in use.
https://rateyourmusic.com/list/TheScien ... libraries/Hope this helps you figure out if you want or need it (to those less familiar with it). There are some sampled synths that use Kontakt so you might get access to some great retro analog or current synths that way too.