Invisalign is by far the most comfortable because you can take them off. You have to wear them for about 22 hours a day. This means you'll only be taking them out to eat and brush your teeth. You will forget you even have them on. Now, they will work for whatever crowding. For treatment time, it depends on your case. Average cost for treatment is from €2,000 to €7,000.
The lingual braces [Incognito brand is by 3M] are already an oldest technique. They work as well as traditional braces, but require more customization and are initially very uncomfortable especially in the first weeks (lingual braces can be very harsh on your tongue). They are more expensive, from €5,000 -€12,000, and complicated to place but produce similar results as traditional braces. Treatment time averages depends on your case.
Clear transparent braces are initially use for teenager but some orthodontist use them for adult. Cost is about €1,000 less than an Invisalign treatment.
In the initial consultation, your orthodontist will define the best option for you. Also, for any case, add 12 months if you need any extractions.
Prices given here are only given to inform you and may change from one office to another one. You may ask to your orthodontist an estimate.