who are the top mix engineers in trap segment? I imagine there's some names that exclusive to that area, and perhaps even carry a signature style of their own?

good question.
-The dude Alex Tumay has built a big name/rep for himself off of recording/engineering Young Thug (among others) stuff. Has a pretty big online following and drops a lot of production/engineering gems.
-Grand Hustle used to have some in-house guys that were great. There was a kid named Daniel who was a recording/mixing engineer for them back in the day (think 8'ish years ago, the Young LA days..) who is very talented producer/engineer. He does his own DJ/production thing under the name "Heroes x Villains" now and is pretty big in that scene. Dude has always been a talented producer and engineer across a ton of different genres. I don't know who was the in-house guys at Grand Hustle back in 2005 or so but whoever they were, were held to a high regard by the teachers at the (janky) engineering school I went to. We used to reference "Shoulder Lean" all the time as a near-perfect hip-hop mix (juxtaposed with Jay's "Show Me What Ya Got" which was given as an example of a horrible mix). Even these old rock engineers who taught there who worked with bands like Sonic Youth and shyt back in the day were like



when it came to the Shoulder Lean mix/master...they were obsessed
-I forget the dudes name I think it's "Ry Engineering" who did a lot of the Bricksquad era Gucci/Waka stuff and also mixes for 808 Mafia... he is another highly regarded and popular trap mixing and recording engineer. I've seen some recording sessions on youtube of him recording vocals for dudes like Gucci and French Montana - he deserves a gold medal for the amount of work that would take reigning in these guys.
Toomp's stuff always sounded really clean and good.
Most producers can and should be able to get a good sounding mix of a beat so when vocals are added and it's given to the engineer for a final mix, it's not a total mess. It's generally the older producers who came up when taking more pride in the craft was a thing, versus the "making hitz" and "mixing? I just throw a limiter on the master channel and make everything loud

" mentality some of the younger producers have today.
Some of the best mixing/engineering can be found in electronic music - especially in Drum and Bass where a lot of underground guys HAVE to mix their stuff on their own and have it 'dancefloor ready'. In fact an old Drum and Bass producer from the 90s/early 2000s (DJ Hive) runs a mixing and mastering house in LA now and is doing really well. Dude is an insane engineer. He has done mastering for a TON of people in all genres. Mastering is a whole nother animal and that's where the $ is at because it's way more of a rare skill to have those 'mastering ears' than anything else.