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External as a boot drive mainly makes sense for desktops or laptops that are primarily used like a desktop. If you use your laptop on the go you should try an internal SSD first before considering whether you really want to boot off an external.
 
ospeand wrote:
"I saw also that some forums are suggesting using an external ssd connected through tunderbolt as the main drive could be an option, I am confident could be more expensive but at least would have a drive that can be reused if I change machine; does anyone has experience/suggestion with this?"

You have some researching and learning to do.
We can't do it for you.
So... get busy.

Having said that...
You CAN boot and run from an external USB3 SSD, and it will be considerably faster that booting from the internal platter-based hard drive.
You will get read speeds around 420MBps this way.

You need either a pre-assembled USB3 SSD, or, you can get a "bare" 2.5" SSD and an enclosure, and "create your own".

Then, use CarbonCopyCloner (FREE to download and use for 30 days) to "clone" the contents of the internal HDD to the USB3 SSD.

Then, set it to be the new boot drive using the startup disk preference pane.

HOWEVER...
If you choose to install an internal "blade" SSD, you can get reads up around 700MBps -- somewhat faster.
But it's a little more work, you have to remove the bottom cover, and then put in a small bracket (I think), goes in easy, connect to motherboard.

Again, it's UP TO YOU to "do the research"...
 
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