Hi hassled 
I am a gel nail tech so hopefully can shed some light.
You can have 3 different types of gel nails/extentions.
1 - gel polish (any colour/design) painted on as normal to your natural nail, cured by a UV light - usually 2/3mins per coat of paint. This is good for helping your nails grow out, if you like shorter nails or if you want them to look as natural as possible. Depending on how quick your nails grow these can last upto 6 weeks without chipping/looking worn but would recommend redoing every 3weeks to keep them looking smart.
2 - false tips (plastic) are stuck to your natural nail and then cut and filed to your chosen length and shape then built up with a uv gel and painted with uv polish. This process takes a little while longer as you are adding the tips unlike directly onto natural nail.
3 - No fake tips stuck to your nail but length added by building a false nail from the uv gel instead. Follewed again by uv polish in any colour/design of your choice.
Any of these options will 'grow out' as your natural nail grows but is no different to how your nails would look wearing normal polish and growing.
I generally do my clients every 4 weeks, some of them every 2-3 if their nails grow quick. I do my own anywhere between every 2-5 weeks depending.
If you decide you no longer want the polish all you have to do is gently buff/fule the polish to take the shine off, dunk a cotton wool ball in some acetone, place it over the nail, use a small square of foil and wrap it over your finger tip as tight as possible to hold the wool in place, leave for 10minutes and then wipe away the polish. If it doesnt come off after that time just repeat the process until it is removed.
If good quality products are used, a primer and no files/drills it really should not affect your natural nails strength that much.
I would suggest looking on google/instagram/pintrest for UV nail art to get some ideas of what is possible - most of my clients are always coming to me with new design ideas.
Sorry for the essay, but hope it helps! 