This refers to someone who lives well and makes sure that everyone knows it - he drives a flashy car, wears flashy jewelry, dates flashy women, etc., and does everything in his power to show off his wealth.

жизнь на широкую ногу - doesn't convey the negative connotation. it simply means a fancy lifestyle.

Thanks for the explanation.

жить напоказ - обычно смысл другой - https://www.google.com/search?q=жить+напоказ

"doesn't convey the negative connotation" - не согласен.

Can I use "flashy words"?

не понимаю

Это к Uly вопрос. Можно ли использовать выражение "flashy words"?

Я не Uly, но могу спросить: "Использовать где?"
Думаю, он задал бы этот же вопрос.

А если вообще, то легко проверить и самому - https://www.google.com/search?q="flashy+words"

https://www.google.com/search?q=%22flashy%20words%22&tbm=bks&lr=lang_en - это только книги

Anything you use to impress people is considered flashy.

However usually it refers to expensive things that you show off with.