Tell me about old European cut diamonds

Hi

I am looking for a diamond for my engagement ring (planning to make a classic Tiffany setting in yellow or rose gold, about 0.8 carats or 5.70-6.00 + mm in diameter).

I thought I would have an ideal cut, good color, eye clan, round brilliant. However, I have seen some videos of old European cut rounds and pillows and they look like they have more sparkle and reflect a rainbow.

Are old European cuts more ingenious? Who sells them? What should I look for? What should I stay away from?

Thanks in advance for all the knowledge