Clean install in BIOS Legacy Mode or UEFI?

Hello, currently I have the upgraded Windows 10 Pro Spanish 32-bit activated from Windows 7 Spanish OEM 32-bit on a 2011 HP ProBook 6550b LATAM which I guess has the digital entitlement since no keys were entered. I would like to clean install & format the drive using the USB Windows Pro 10 media & Brink's Windows 10 - Clean Install tutorial and have 3 questions:

Q1: checking in System Information is says the OS was installed in BIOS Legacy Mode but in the Boot menu there is an option to select UEFI instead. Which one is the best?

Q2: if clean install is done with an English US version instead of Spanish will I loose the activation?

Q3: I tried changing the display & speech language option to English in my current Spanish OS, rebooted several times and get the persistent Windows Search "these results may be incomplete" error after Indexing is completed as reported in other threads while it works fine when reverting back to Spanish display mode. Anybody knows if that bug is solved in the anniversary update?

Thanks!

Q1: UEFI is better but you have to install 64bit. Older pcs may not be 64bit compatible.

Q2: if normal multi-language, will be fine.

Q3: sounds like you install is corrupted. An upgrade should work fine.

NavyLCDR said:

I have two computer's with 32-bit installed in UEFI mode. NEXTBOOK Flexx 10 tablet and Azulle Access stick computer.

Yes but those devices use special 32bit bootloaders. The uefi standard does not specify the bit type actually - that is hardware dependent.

My tablet uses 32bit even though cpu is 64bit. It cannot be changed as the bootloader is flashed into the firmware.
Similarly virtually all uefi pcs use a firmware flashed 64bit bootloader.