I have a 2017 Leon FR 1.8TSI, manual, with a "Stage 1 tune". It's is the SC model and I had the map done earlier this year at 63k, now at 69k, and is making just under 250bhp and 350nm of torgue. Here's my experience:
Stage 1 can be done completely stock (as long as its well maintained and no major issues) however I bought a full racingline intake kit + turbo muffler delete for the noise, OEM+ look, and that little bit of extra power. I installed this before having it mapped for obvious reasons and its the only mod I have, so I;m on the stock clutch.
Took it to JFAutomotive in Kent, very friendly and informative guys and it took them a few hours. They had reduced the torgue at the lower end to avoid any clutch slipping as you mentioned, but these cars also make slightly more power/torgue that they are "advertised" as (I think mine was around 190bhp.
Honestly, as others have already said the clutch slipping is either due to a bad map or the clutch is on it's way out (maybe from people ripping the life out of them) but if you don;t notice any clutch issues then you should be good to go. Just go to a reputable company like JF or another, avoid these back-alley mobile tuners and flash ECUs, its worth the money for a map + dyno run for enjoyment and longevity. Have fun!