Q:

How are 连绵词 used in modern Chinese?

A concise definition of 连绵词 I found is

an alliterative and echotic biome

e.g. ： 

窈窕
徘徊
孜孜

Is this group perceived as sth. distinctive with unique rules how or under which circumstances to use them? 
How are they perceived in terms of aesthetics, e.g. do they convey a poetic or archaic connotation?

A:

聯綿詞 

聯綿詞 is a terminology in Chinese phonology. They are still functional 詞(compound words). 

do they convey a poetic or archaic connotation?

Some 聯綿詞 adjective and verb do sound poetic or archaic (e.g 玲瓏, 翩翩, 叮嚀,  拮据). 
Some 聯綿詞 adjective and verb had become common day-to-day words (e.g. 荒唐, 嘮叨, 累贅, 凌厲)
Almost all 聯綿詞 noun are common day-to-day words (e.g. 琵琶, 橄欖, 鞦韆, 蝴蝶)

