Apologies for not writing enough about the academic technicalities behind the various types of wipes in TWRP.
Just to repeat for clarity, you only need to use the format data button (wiping your locksreen credentials) when coming from a NATIVE MIUI ROM (that's china, global, developer) to xiaomi.eu ROM, not when you already have xiaomi.EU installed. When you are upgrading xiaomi.eu you have options of dirty flash (install without any wipe), or clean flash (install with 'factory reset' as TWRP calls it - wiping cache, dalvik, data partitions).
Hu mcsmartie
i have 3 questions to ask, about Xiaomi flashing generical devices :
- in recovery, passing from Global to Xiaomi.eu ( weekly or stable ), after have made Format data, and reboot to recovery, and then Advanced wipe, in many twrp i can choose this 5 options

alvink/ART cache, Cashe, Vendor, Data, Internal storage, can i wipe this 5 things without have problems ?
- when i want pass from xiaomi.eu weekly to xiaomi.eu stable, i have to make wipe of the 5 things above ? For me is not important to loss something in the phone ( photos, passwords, ....).
- i have some smartphones to unlock, last unlock was made 3 days ago, for make another unlock i have read that i can make only 1 unlock in one month, but when are passed 15 days, can i begin to try to unlock the phone for not have to wait more time ( example 360 hours ) when the month will be finished ?
Thank's