Hi - Much better on the profile!
Ok - Gels
Soak off gels are a soft system - designed to feel more 'natural', they are more flexible, but also more likely to be damaged by environmental factors (cleaning products etc)
They can easily be removed by soaking with Acetone based removers
Hard Gels (buff off gels)
Are a non porous gel, more like acrylic in finished result, strong for enhancement and length addition. Can not be soaked off - must be filed off.
Product chemistry - Nail enhancements are all based on the same family of chemicals, methacrylates, so in essense the main difference is the way they feel and level of strength the provide.
Brand wise, there are hundreds... many are cheap, and this is how they often last...
High grade (professional brands) are more restrictive on supply, most require proof of qualification. These products use high quality ingredients (and often proprietary technology) and as such, they want this product only in the right hands...
As you are training, some will allow you sample quantities so you can get a feel for different products. CND is the global leader for science, products and has an award winning global training programme
CND - Sweet Squared
I hope this helps you a little, my only advise is master one system type from one brand at a time...
Don't become a 'jack of all trades - master of none' by chopping and changing so much while trying to learn that you end up confused