To answer the hearability question - I'd say yes, you likely will.
More important is to [1] locate the tweeters properly...
That guy has a Vanagon so didn't waste any effort to get something 3D printed - it is the correct position tho.
[2] use a high quality cross-over
[3] use an amp that can drive the speakers - a powerful amp
[4] avoid mp3 & Bluetooth
and most importantly [5] use a large amount of dampening material and isolation in the cabin