Windows 10 USB installation

So I need a legit copy of Win 10 for my new build and the cheapest way for me is to buy the key for it from Kinguin. Can I make a clean installation with no problems if I download the ISO file from Microsoft and put it to a USB drive? Is it like installing Win 8 where you just type the key in when you are installing and you are good to go? BTW there was no mention if the key is for 32 bit or 64 bit version, but I guess I can use the key for either one.

Can't guarantee there will be no problems. It is recommended that you do the upgrade method instead of a clean install. It is the exact same as installing any other windows OS from a USB. I have done a clean install of Win10 and there were problems b/c it does not come with specific drivers for ODD and other legacy software. Upgrading method will preserve these unless it is just not compatible. And keys are not architecture specific to the best of my knowledge.

So should I buy a Win 8.1 key and upgrade from that?

Read this before you start.

I recently did this.
Download the Microsoft media creation tool.
Download the iso from Microsoft.
Use the media creation tool to put the iso on a usb drive.
Use your key when installing the OS.
It worked flawlessly for me.

The only thing I would add to what has been posted already, is burn the .iso using Rufus, it should be faster than the MS official tool. Otherwise it should work fine...I did my win10 install this way. USB, enter key, done. Just make sure your internet connection is disabled when you install.

Why should you disable internet connection?

If you don't have win7 or 8 to upgrade from, and you are buying OS anyway, then buy license of 10 to save yourself from installing win8, upgrade and then installing clean and hoping it will activate.
Use Media creation tool with any USB key or DVD.
I upgraded about 30 machines to win10 and 3 just don't want to activate after clean install afterwards.

It runs a completely different installation when run offline. Not only does it give Microsoft less of an opportunity to set up the built in adware, it actually stops a whole range of evil things from happening. I heard about this on several InfoSec podcasts, but I always run installs offline anyway for patch/update control.